refactor(2): Core Platform abstractions (IProcessRunner/IMediaMuxer + Desktop impls) - Hls/Dash/YtDlp through injection seams, threading contract documented (66 tests GREEN)

VideoDownloader.Core/Dash/DashDownloader.cs

@@ -15,7 +15,11 @@ public class DashDownloader
     private readonly HttpClient _http;
     private readonly AppConfig _config;
 
-    public DashDownloader(HttpClient http, AppConfig config) { _http = http; _config = config; }
+    private readonly Platform.IMediaMuxer _muxer;
+
+    public DashDownloader(HttpClient http, AppConfig config) : this(http, config, Platform.DesktopMediaMuxer.Default) { }
+
+    public DashDownloader(HttpClient http, AppConfig config, Platform.IMediaMuxer muxer) { _http = http; _config = config; _muxer = muxer; }
 
     public async Task<string> DownloadAsync(Uri mpdUrl, string outputBase,
         IProgress<DownloadProgress>? progress = null, CancellationToken ct = default)
@@ -40,7 +44,7 @@ public class DashDownloader
             throw new InvalidOperationException($"MPD 조회/파싱 실패: {e.Message}", e);
         }
 
-        var ffmpeg = ResolveFfmpeg()
+        var ffmpeg = _muxer.ResolveFfmpeg(_config)
             ?? throw new InvalidOperationException("DASH 다운로드에는 ffmpeg가 필요합니다 (시스템 PATH 또는 설정의 ffmpeg 경로).");
 
         var final = outputBase + ".mp4";
@@ -48,7 +52,7 @@ public class DashDownloader
         bool success = false;
         try
         {
-            await RunFfmpegDashAsync(ffmpeg, mpdUrl, final, durationSec, progress, ct);
+            await _muxer.DownloadDashAsync(ffmpeg, mpdUrl, final, durationSec, _http, progress, ct);
             if (!File.Exists(final) || new FileInfo(final).Length == 0)
                 throw new InvalidOperationException("ffmpeg 출력 파일이 비었거나 없습니다.");
             success = true;
@@ -61,94 +65,4 @@ public class DashDownloader
         }
     }
 
-    /// <summary>ffmpeg -i mpdUrl -c copy out.mp4. -progress pipe:1 로 time= 를 파싱해 진행률.</summary>
-    private async Task RunFfmpegDashAsync(string ffmpeg, Uri mpdUrl, string output, double durationSec,
-        IProgress<DownloadProgress>? progress, CancellationToken ct)
-    {
-        Process? proc = null;
-        try
-        {
-            var psi = new ProcessStartInfo(ffmpeg)
-            {
-                UseShellExecute = false, CreateNoWindow = true,
-                RedirectStandardError = true, RedirectStandardOutput = true,
-            };
-            psi.ArgumentList.Add("-y");
-            psi.ArgumentList.Add("-hide_banner");
-            psi.ArgumentList.Add("-loglevel"); psi.ArgumentList.Add("error");
-            psi.ArgumentList.Add("-progress"); psi.ArgumentList.Add("pipe:1");
-            // #6 HTTP 옵션은 -i 앞(per-input AVOption) — .NET 사전검증에 쓴 UA/Referer/쿠키를 ffmpeg 에 전달.
-            //    토큰/Referer 인증 CDN(maccms 계열) 에서 ffmpeg 기본 UA 로 403 이 나는 것을 방지.
-            AddFfmpegHttpOptions(psi, _http);
-            psi.ArgumentList.Add("-i"); psi.ArgumentList.Add(mpdUrl.ToString());
-            psi.ArgumentList.Add("-c"); psi.ArgumentList.Add("copy");
-            psi.ArgumentList.Add("-movflags"); psi.ArgumentList.Add("+faststart");
-            psi.ArgumentList.Add(output);
-            proc = Process.Start(psi) ?? throw new InvalidOperationException("ffmpeg 시작 실패");
-
-            var stderrTask = proc.StandardError.ReadToEndAsync(ct);
-            string? line;
-            while ((line = await proc.StandardOutput.ReadLineAsync(ct)) != null)
-            {
-                if (line.StartsWith("out_time_ms=", StringComparison.Ordinal) && durationSec > 0)
-                {
-                    if (long.TryParse(line.AsSpan("out_time_ms=".Length), out long us) && us >= 0)
-                    {
-                        var pct = Math.Min(99, us / 1_000_000.0 * 100.0 / durationSec);
-                        progress?.Report(new DownloadProgress(0, 0, "downloading", pct, $"{us / 1_000_000.0:F0}/{durationSec:F0}s"));
-                    }
-                }
-                if (line == "progress=end") break;
-            }
-            await proc.WaitForExitAsync(ct);
-            var stderr = await stderrTask;
-            if (proc.ExitCode != 0)
-            {
-                var msg = string.IsNullOrWhiteSpace(stderr) ? $"exit {proc.ExitCode}" : stderr.Trim();
-                throw new InvalidOperationException($"ffmpeg DASH 다운로드 실패: {msg}");
-            }
-        }
-        finally
-        {
-            try { if (proc is { HasExited: false }) proc.Kill(entireProcessTree: true); } catch { }
-        }
-    }
-
-    /// <summary>#6 HttpClient 에 설정된 UA/Referer/Cookie 를 ffmpeg HTTP AVOption(-i 앞) 으로 전달.
-    /// -user_agent/-referer/-headers: 토큰·Referer 인증 CDN(maccms 계열) 에서 403 을 막는다.</summary>
-    private static void AddFfmpegHttpOptions(ProcessStartInfo psi, HttpClient http)
-    {
-        var ua = http.DefaultRequestHeaders.UserAgent.ToString();
-        if (!string.IsNullOrWhiteSpace(ua)) { psi.ArgumentList.Add("-user_agent"); psi.ArgumentList.Add(ua); }
-
-        if (http.DefaultRequestHeaders.Referrer is { } refUri)
-        {
-            psi.ArgumentList.Add("-referer");
-            psi.ArgumentList.Add(refUri.IsAbsoluteUri ? refUri.AbsoluteUri : refUri.ToString());
-        }
-
-        if (http.DefaultRequestHeaders.TryGetValues("Cookie", out var cookies))
-        {
-            var cookieHeader = string.Join("; ", cookies);
-            if (!string.IsNullOrWhiteSpace(cookieHeader))
-            {
-                psi.ArgumentList.Add("-headers");
-                // ffmpeg -headers: 각 헤더를 \r\n 으로 종료한 전체 값.
-                psi.ArgumentList.Add("Cookie: " + cookieHeader + "\r\n");
-            }
-        }
-    }
-
-    private string? ResolveFfmpeg()
-    {
-        if (!string.IsNullOrWhiteSpace(_config.FfmpegPath) && File.Exists(_config.FfmpegPath))
-            return _config.FfmpegPath;
-        var name = OperatingSystem.IsWindows() ? "ffmpeg.exe" : "ffmpeg";
-        foreach (var d in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator))
-        {
-            var p = Path.Combine(d.Trim('"'), name);
-            if (File.Exists(p)) return p;
-        }
-        return null;
-    }
 }

VideoDownloader.Core/Hls/HlsDownloader.cs

@@ -17,7 +17,11 @@ public class HlsDownloader
     private readonly AppConfig _config;
     private readonly ConcurrentDictionary<Uri, byte[]> _keys = new();
 
-    public HlsDownloader(HttpClient http, AppConfig config)
+    private readonly Platform.IMediaMuxer _muxer;
+
+    public HlsDownloader(HttpClient http, AppConfig config) : this(http, config, Platform.DesktopMediaMuxer.Default) { }
+
+    public HlsDownloader(HttpClient http, AppConfig config, Platform.IMediaMuxer muxer)
     {
         _http = http;
         _config = config;
@@ -182,7 +186,7 @@ public class HlsDownloader
         string merged, string outputBase, bool isFmp4,
         IProgress<DownloadProgress>? progress, CancellationToken ct)
     {
-        var ffmpeg = ResolveFfmpeg();
+        var ffmpeg = _muxer.ResolveFfmpeg(_config);
         if (ffmpeg != null)
         {
             var final = outputBase + ".mp4";
@@ -191,7 +195,7 @@ public class HlsDownloader
             progress?.Report(new DownloadProgress(0, 0, "remuxing"));
             try
             {
-                await RunFfmpegAsync(ffmpeg, merged, final, ct);
+                await _muxer.RemuxAsync(ffmpeg, merged, final, ct);
                 if (File.Exists(final) && new FileInfo(final).Length > 0)
                 {
                     File.Delete(merged);
@@ -213,49 +217,5 @@ public class HlsDownloader
         return keep;
     }
 
-    private string? ResolveFfmpeg()
-    {
-        if (!string.IsNullOrWhiteSpace(_config.FfmpegPath) && File.Exists(_config.FfmpegPath))
-            return _config.FfmpegPath;
-        var name = OperatingSystem.IsWindows() ? "ffmpeg.exe" : "ffmpeg";
-        foreach (var d in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator))
-        {
-            var p = Path.Combine(d.Trim('"'), name);
-            if (File.Exists(p)) return p;
-        }
-        return null;
-    }
 
-    // #2 stderr/stdout 파이프를 동시에 드레인(데드락 방지), 종료 보장(좀비 방지), 실패 시 예외 throw
-    // #10 stdout 드레인 태스크도 관측 — 취소 시 미관측(faulted) 태스크가 되지 않도록 finally 에서 await.
-    private static async Task RunFfmpegAsync(string ffmpeg, string input, string output, CancellationToken ct)
-    {
-        Process? proc = null;
-        Task<string>? stdoutTask = null;
-        try
-        {
-            var psi = new ProcessStartInfo(ffmpeg)
-            {
-                UseShellExecute = false,
-                CreateNoWindow = true,
-                RedirectStandardError = true,
-                RedirectStandardOutput = true,
-            };
-            foreach (var a in new[] { "-y", "-hide_banner", "-loglevel", "error", "-i", input, "-c", "copy", output })
-                psi.ArgumentList.Add(a);
-            proc = Process.Start(psi) ?? throw new InvalidOperationException("ffmpeg 시작 실패");
-            var stderrTask = proc.StandardError.ReadToEndAsync(ct);
-            stdoutTask = proc.StandardOutput.ReadToEndAsync(ct); // stdout 도 드레인(데드락 방지)
-            await proc.WaitForExitAsync(ct);
-            var stderr = await stderrTask;
-            if (proc.ExitCode != 0)
-                throw new InvalidOperationException($"ffmpeg 리먹스 실패(exit {proc.ExitCode}): {stderr.Trim()}");
-        }
-        finally
-        {
-            try { if (proc is { HasExited: false }) proc.Kill(entireProcessTree: true); } catch { }
-            // #10 드레인 태스크 관측 (취소/OCE/EOF 시 폭발 무시)
-            try { if (stdoutTask is not null) await stdoutTask; } catch { }
-        }
-    }
 }

VideoDownloader.Core/Platform/MediaMuxer.cs

@@ -0,0 +1,111 @@
+using System.Net.Http;
+using VideoDownloader.Core.Config;
+using VideoDownloader.Core.Models;
+
+namespace VideoDownloader.Core.Platform;
+
+/// <summary>
+/// 미디어 병합/리먹스 추상화(재구성 ②). ffmpeg 서브프로세스가 필요한 두 지점
+/// (HLS 세그먼트 리먹스 · DASH ffmpeg-native 다운로드)를 캡슐화한다.
+/// 모바일 호스트는 네이티브 구현으로 대체 주입 가능.
+/// </summary>
+public interface IMediaMuxer
+{
+    /// <summary>ffmpeg -c copy 리먹스(HLS .ts→.mp4, fMP4 병합). 실패 시 stderr 포함 예외.</summary>
+    Task RemuxAsync(string ffmpeg, string input, string output, CancellationToken ct);
+
+    /// <summary>ffmpeg -i &lt;mpd&gt; DASH 네이티브 다운로드. -progress pipe:1 진행률 파싱.</summary>
+    Task DownloadDashAsync(string ffmpeg, Uri mpdUrl, string output, double durationSec,
+        HttpClient http, IProgress<DownloadProgress>? progress, CancellationToken ct);
+
+    /// <summary>ffmpeg 실행 파일 해결(설정 → PATH). 없으면 null.</summary>
+    string? ResolveFfmpeg(AppConfig config);
+}
+
+/// <summary>데스크톱 구현 — IProcessRunner 기반. 기존 Hls/Dash 다운로더의 인자·진행 파싱을 그대로 보존.</summary>
+public sealed class DesktopMediaMuxer : IMediaMuxer
+{
+    public static DesktopMediaMuxer Default { get; } = new(DesktopProcessRunner.Default);
+
+    private readonly IProcessRunner _runner;
+    public DesktopMediaMuxer(IProcessRunner runner) => _runner = runner;
+
+    public async Task RemuxAsync(string ffmpeg, string input, string output, CancellationToken ct)
+    {
+        var res = await _runner.RunAsync(new ProcessSpec(ffmpeg,
+            new[] { "-y", "-hide_banner", "-loglevel", "error", "-i", input, "-c", "copy", output }), null, ct);
+        if (res.ExitCode != 0)
+            throw new InvalidOperationException($"ffmpeg 리먹스 실패(exit {res.ExitCode}): {res.Stderr.Trim()}");
+    }
+
+    public async Task DownloadDashAsync(string ffmpeg, Uri mpdUrl, string output, double durationSec,
+        HttpClient http, IProgress<DownloadProgress>? progress, CancellationToken ct)
+    {
+        var args = new List<string>
+        {
+            "-y", "-hide_banner", "-loglevel", "error", "-progress", "pipe:1",
+        };
+        AddFfmpegHttpOptions(args, http);
+        args.Add("-i");
+        args.Add(mpdUrl.ToString());
+        args.Add("-c");
+        args.Add("copy");
+        args.Add("-movflags");
+        args.Add("+faststart");
+        args.Add(output);
+
+        var res = await _runner.RunAsync(new ProcessSpec(ffmpeg, args), (stream, line) =>
+        {
+            if (stream != "out" || durationSec <= 0) return;
+            if (line.StartsWith("out_time_ms=", StringComparison.Ordinal)
+                && long.TryParse(line.AsSpan("out_time_ms=".Length), out var us) && us >= 0)
+            {
+                var pct = Math.Min(99, us / 1_000_000.0 * 100.0 / durationSec);
+                progress?.Report(new DownloadProgress(0, 0, "downloading", pct, $"{us / 1_000_000.0:F0}/{durationSec:F0}s"));
+            }
+        }, ct);
+
+        if (res.ExitCode != 0)
+        {
+            var msg = string.IsNullOrWhiteSpace(res.Stderr) ? $"exit {res.ExitCode}" : res.Stderr.Trim();
+            throw new InvalidOperationException($"ffmpeg DASH 다운로드 실패: {msg}");
+        }
+    }
+
+    public string? ResolveFfmpeg(AppConfig config)
+    {
+        if (!string.IsNullOrWhiteSpace(config.FfmpegPath) && File.Exists(config.FfmpegPath))
+            return config.FfmpegPath;
+        var name = OperatingSystem.IsWindows() ? "ffmpeg.exe" : "ffmpeg";
+        foreach (var d in (Environment.GetEnvironmentVariable("PATH") ?? "").Split(Path.PathSeparator))
+        {
+            var p = Path.Combine(d.Trim('"'), name);
+            if (File.Exists(p)) return p;
+        }
+        return null;
+    }
+
+    /// <summary>HttpClient 의 UA/Referer/Cookie 를 ffmpeg HTTP AVOption(-i 앞) 으로 전달(토큰 CDN 403 방지).</summary>
+    private static void AddFfmpegHttpOptions(List<string> args, HttpClient http)
+    {
+        var ua = http.DefaultRequestHeaders.UserAgent.ToString();
+        if (!string.IsNullOrWhiteSpace(ua)) { args.Add("-user_agent"); args.Add(ua); }
+
+        if (http.DefaultRequestHeaders.Referrer is { } refUri)
+        {
+            args.Add("-referer");
+            args.Add(refUri.IsAbsoluteUri ? refUri.AbsoluteUri : refUri.ToString());
+        }
+
+        if (http.DefaultRequestHeaders.TryGetValues("Cookie", out var cookies))
+        {
+            var cookieHeader = string.Join("; ", cookies);
+            if (!string.IsNullOrWhiteSpace(cookieHeader))
+            {
+                args.Add("-headers");
+                // ffmpeg -headers: 각 헤더를 \r\n 으로 종료한 전체 값.
+                args.Add("Cookie: " + cookieHeader + "\r\n");
+            }
+        }
+    }
+}

VideoDownloader.Core/Platform/ProcessModels.cs

@@ -0,0 +1,83 @@
+using System.Text;
+namespace VideoDownloader.Core.Platform;
+
+/// <summary>프로세스 실행 명세. EnvPrefix 값은 기존 값 앞에 붙는다(PATH 선두 주입용).</summary>
+public sealed record ProcessSpec(
+    string ExePath,
+    IReadOnlyList<string> Args,
+    IReadOnlyDictionary<string, string>? EnvPrefix = null);
+
+/// <summary>프로세스 실행 결과. Stdout/Stderr 은 전체 누적(라인 탭과 별개).</summary>
+public sealed record ProcessResult(int ExitCode, string Stdout, string Stderr);
+
+/// <summary>
+/// 프로세스 실행 추상화(재구성 ② / M0 전제). 모바일(iOS)에선 구현체를 주입하지 않고
+/// 데스크톱(Win/macOS/Linux)은 DesktopProcessRunner 사용. 단일 프리미티브로
+/// yt-dlp 라인 스트리밍 · -J 캡처 · ffmpeg 리먹스/DASH 진행 파싱을 모두 커버한다.
+/// </summary>
+public interface IProcessRunner
+{
+    /// <summary>실행. onLine?(stream:"out"|"err", line) 실시간 탭. 취소 시 트리 킬.</summary>
+    Task<ProcessResult> RunAsync(ProcessSpec spec, Action<string, string>? onLine, CancellationToken ct);
+}
+
+/// <summary>데스크톱 구현 — 기존 YtDlpRunner/HlsDownloader 의 검증된 안전 규칙:
+/// stdout/stderr 동시 드레인(데드락 방지), 취소/실패 시 entireProcessTree 킬, 인자 배열 전달.</summary>
+public sealed class DesktopProcessRunner : IProcessRunner
+{
+    public static DesktopProcessRunner Default { get; } = new();
+
+    public async Task<ProcessResult> RunAsync(ProcessSpec spec, Action<string, string>? onLine, CancellationToken ct)
+    {
+        System.Diagnostics.Process? proc = null;
+        try
+        {
+            var psi = new System.Diagnostics.ProcessStartInfo(spec.ExePath)
+            {
+                UseShellExecute = false,
+                CreateNoWindow = true,
+                RedirectStandardError = true,
+                RedirectStandardOutput = true,
+            };
+            foreach (var a in spec.Args) psi.ArgumentList.Add(a);
+            if (spec.EnvPrefix != null)
+            {
+                foreach (var (key, prefix) in spec.EnvPrefix)
+                {
+                    var cur = psi.Environment.TryGetValue(key, out var existing) ? (existing ?? "") : "";
+                    psi.Environment[key] = prefix + Path.PathSeparator + cur;
+                }
+            }
+
+            proc = System.Diagnostics.Process.Start(psi)
+                ?? throw new InvalidOperationException($"{spec.ExePath} 시작 실패");
+            await using var _ = ct.Register(() =>
+            {
+                try { if (!proc.HasExited) proc.Kill(entireProcessTree: true); } catch { }
+            });
+
+            var stdout = new System.Text.StringBuilder();
+            var stderr = new System.Text.StringBuilder();
+            var outTask = TapAsync(proc.StandardOutput, "out", stdout, onLine, ct);
+            var errTask = TapAsync(proc.StandardError, "err", stderr, onLine, ct);
+            await proc.WaitForExitAsync(ct);
+            await Task.WhenAll(outTask, errTask);
+            return new ProcessResult(proc.ExitCode, stdout.ToString(), stderr.ToString());
+        }
+        finally
+        {
+            try { if (proc is { HasExited: false }) proc.Kill(entireProcessTree: true); } catch { }
+        }
+    }
+
+    private static async Task TapAsync(StreamReader reader, string stream, StringBuilder acc,
+        Action<string, string>? onLine, CancellationToken ct)
+    {
+        string? line;
+        while ((line = await reader.ReadLineAsync(ct)) != null)
+        {
+            acc.AppendLine(line);
+            if (onLine != null && !string.IsNullOrWhiteSpace(line)) onLine(stream, line);
+        }
+    }
+}

VideoDownloader.Core/Social/YtDlpRunner.cs

@@ -70,11 +70,12 @@ public static class YtDlpRunner
     }
 
     /// <summary>설치된 yt-dlp 버전 문자열("2026.03.17"). 알 수 없으면 null.</summary>
-    public static async Task<string?> GetVersionAsync(string exe, CancellationToken ct)
+    public static async Task<string?> GetVersionAsync(string exe, CancellationToken ct,
+        Platform.IProcessRunner? runner = null)
     {
         try
         {
-            var (exit, stdout, _) = await RunCaptureAsync(exe, new[] { "--version" }, ct);
+            var (exit, stdout, _) = await RunCaptureAsync(exe, new[] { "--version" }, ct, runner);
             if (exit != 0) return null;
             var first = stdout.Trim().Split('\n', StringSplitOptions.TrimEntries)[0];
             return string.IsNullOrWhiteSpace(first) ? null : first;
@@ -126,89 +127,24 @@ public static class YtDlpRunner
         return null;
     }
 
-    /// <summary>yt-dlp 자식 프로세스 PATH 앞에 ToolsDir 를 추가 → 번들 deno.exe(EJS n 챌린지 해석용) 를 yt-dlp 가 자동 발겑.
-    /// 시스템 PATH 는 건드리지 않고 이 프로세스에만 적용. ffmpeg/yt-dlp 등 다른 번들 도구 발견에도 보조.</summary>
-    private static void PrependToolsToPath(ProcessStartInfo psi)
-    {
-        try
-        {
-            var cur = psi.Environment.TryGetValue("PATH", out var p) ? (p ?? "") : "";
-            psi.Environment["PATH"] = ToolsDir + Path.PathSeparator + cur;
-        }
-        catch { } // UseShellExecute=true 등 예외 시 무시(본 프로젝트에선 항상 false)
-    }
-
-    /// <summary>프로세스 실행. onLine(stream, line): stream="out"|"err". 취소 시 트리 킬.</summary>
+    /// <summary>프로세스 실행. onLine(stream, line): stream="out"|"err". 취소 시 트리 킬.
+    /// 재구성 ②: IProcessRunner 주입 가능(테스트/모바일) — 기본 DesktopProcessRunner.</summary>
     public static async Task<int> RunAsync(string exe, IEnumerable<string> args,
-        Action<string, string> onLine, CancellationToken ct)
+        Action<string, string> onLine, CancellationToken ct, Platform.IProcessRunner? runner = null)
     {
-        Process? proc = null;
-        try
-        {
-            var psi = new ProcessStartInfo(exe)
-            {
-                UseShellExecute = false,
-                CreateNoWindow = true,
-                RedirectStandardError = true,
-                RedirectStandardOutput = true,
-            };
-            foreach (var a in args) psi.ArgumentList.Add(a);
-            PrependToolsToPath(psi); // 번들 deno.exe 를 yt-dlp 가 발견하도록(EJS n 챌린지 해석)
-
-            proc = Process.Start(psi) ?? throw new InvalidOperationException("yt-dlp 시작 실패");
-            await using var _ = ct.Register(() => { try { if (!proc.HasExited) proc.Kill(entireProcessTree: true); } catch { } });
-
-            // stdout/stderr 를 별개 태스크로 동시 드레인(파이프 버퍼 차면 데드락).
-            var outTask = ReadLinesAsync(proc.StandardOutput, "out", onLine, ct);
-            var errTask = ReadLinesAsync(proc.StandardError, "err", onLine, ct);
-            await proc.WaitForExitAsync(ct);
-            await Task.WhenAll(outTask, errTask);
-            return proc.ExitCode;
-        }
-        finally
-        {
-            try { if (proc is { HasExited: false }) proc.Kill(entireProcessTree: true); } catch { }
-        }
+        var r = runner ?? Platform.DesktopProcessRunner.Default;
+        var res = await r.RunAsync(new Platform.ProcessSpec(exe, args.ToList(),
+            EnvPrefix: new Dictionary<string, string> { ["PATH"] = ToolsDir }), onLine, ct);
+        return res.ExitCode;
     }
 
-    /// <summary>stdout 전체를 하나의 문자열로 캡처(-J JSON 덤프용). stderr 도 버퍼링하며 취소 시 트리 킬.</summary>
+    /// <summary>stdout 전체를 하나의 문자열로 캡처(-J JSON 덤프용). 재구성 ②: 러너 주입 가능.</summary>
     public static async Task<(int Exit, string Stdout, string Stderr)> RunCaptureAsync(
-        string exe, IEnumerable<string> args, CancellationToken ct)
+        string exe, IEnumerable<string> args, CancellationToken ct, Platform.IProcessRunner? runner = null)
     {
-        Process? proc = null;
-        try
-        {
-            var psi = new ProcessStartInfo(exe)
-            {
-                UseShellExecute = false,
-                CreateNoWindow = true,
-                RedirectStandardError = true,
-                RedirectStandardOutput = true,
-            };
-            foreach (var a in args) psi.ArgumentList.Add(a);
-            PrependToolsToPath(psi); // 번들 deno.exe 를 yt-dlp 가 발견하도록(EJS n 챌린지 해석)
-
-            proc = Process.Start(psi) ?? throw new InvalidOperationException("yt-dlp 시작 실패");
-            await using var _ = ct.Register(() => { try { if (!proc.HasExited) proc.Kill(entireProcessTree: true); } catch { } });
-
-            var stdoutTask = proc.StandardOutput.ReadToEndAsync(ct);
-            var stderrTask = proc.StandardError.ReadToEndAsync(ct);
-            await proc.WaitForExitAsync(ct);
-            return (proc.ExitCode, await stdoutTask, await stderrTask);
-        }
-        finally
-        {
-            try { if (proc is { HasExited: false }) proc.Kill(entireProcessTree: true); } catch { }
-        }
-    }
-
-    private static async Task ReadLinesAsync(StreamReader reader, string stream, Action<string, string> onLine, CancellationToken ct)
-    {
-        string? line;
-        while ((line = await reader.ReadLineAsync(ct)) != null)
-        {
-            ct.ThrowIfCancellationRequested();
-            if (!string.IsNullOrWhiteSpace(line)) onLine(stream, line);
-        }
+        var r = runner ?? Platform.DesktopProcessRunner.Default;
+        var res = await r.RunAsync(new Platform.ProcessSpec(exe, args.ToList(),
+            EnvPrefix: new Dictionary<string, string> { ["PATH"] = ToolsDir }), null, ct);
+        return (res.ExitCode, res.Stdout, res.Stderr);
     }
 }