T1-4/T1-7: search engine resolver + site zoom store (TDD RED->GREEN, 32 tests)

VideoDownloader.App/Browser/SearchEngine.cs

@@ -0,0 +1,34 @@
+namespace VideoDownloader.App.Browser;
+
+/// <summary>검색엔진 정의. QueryTemplate 의 {0} 이 URL 인코딩된 검색어로 치환된다.</summary>
+public sealed record SearchEngine(string Name, string Keyword, string QueryTemplate);
+
+/// <summary>기본 프리셋 엔진. Keyword 는 주소창에서 `&lt;키워드&gt; &lt;검색어&gt;` 형태로 즉시 전환에 쓰인다.</summary>
+public static class SearchEngines
+{
+    public static readonly IReadOnlyList<SearchEngine> Presets = new[]
+    {
+        new SearchEngine("Google",     "g",  "https://www.google.com/search?q={0}"),
+        new SearchEngine("Bing",       "b",  "https://www.bing.com/search?q={0}"),
+        new SearchEngine("DuckDuckGo", "d",  "https://duckduckgo.com/?q={0}"),
+        new SearchEngine("Naver",      "n",  "https://search.naver.com/search.naver?query={0}"),
+        new SearchEngine("YouTube",    "yt", "https://www.youtube.com/results?search_query={0}"),
+    };
+
+    public static SearchEngine? FindByName(string? name, IEnumerable<SearchEngine>? extra = null)
+    {
+        var pool = extra != null ? Presets.Concat(extra) : Presets;
+        return pool.FirstOrDefault(e =>
+            string.Equals(e.Name, name, StringComparison.OrdinalIgnoreCase));
+    }
+
+    public static SearchEngine? FindByKeyword(string? keyword, IEnumerable<SearchEngine>? extra = null)
+    {
+        var pool = extra != null ? Presets.Concat(extra) : Presets;
+        return pool.FirstOrDefault(e =>
+            string.Equals(e.Keyword, keyword, StringComparison.OrdinalIgnoreCase));
+    }
+}
+
+/// <summary>주소창 입력에 대한 네비게이션 의도. IsUrl=false 면 Target 은 검색 결과 URL.</summary>
+public sealed record NavigationIntent(bool IsUrl, string Target, string? EngineName = null);