fix(installer): 대용량 NSIS 크래시 해소 — Ollama GPU 런타임 가지치기 + oneClick 전환

- download-ollama.ps1: cuda_v11, cuda_v12, rocm_avx 런타임 삭제 (~1GB 절감)
  첫 실행 시 gemma4:e4b는 CPU로 충분. GPU 가속 필요 시 별도 Ollama 설치 또는 차기 빌드.
- electron-builder.yml nsis: oneClick=true로 전환 — oneClick=false+perMachine=false가
  System.dll 0xc0000005 유발하는 electron-builder 알려진 이슈(#7921) 회피.

apps/desktop/scripts/download-ollama.ps1

@@ -56,12 +56,24 @@ Expand-Archive -Path $TEMP_ZIP -DestinationPath $TEMP_DIR -Force
 
 New-Item -ItemType Directory -Force -Path $DEST_DIR | Out-Null
 
-# zip layout: ollama.exe + lib/ (DLLs). Copy everything.
+# zip layout: ollama.exe + lib/ (runners + DLLs).
+# Prune GPU runners (CUDA v11/v12, ROCm) to keep installer under NSIS 2GB limit.
+# CPU runners (cpu_avx2, cpu_avx) are sufficient for initial bundle; users needing GPU
+# can install Ollama separately or via future builds.
 Get-ChildItem -Path $TEMP_DIR -Force | ForEach-Object {
     Copy-Item $_.FullName -Destination $DEST_DIR -Recurse -Force
     Write-Host ("  copied: {0}" -f $_.Name) -ForegroundColor Green
 }
 
+# Remove heavy GPU runners to stay below NSIS size limits
+$runnersDir = Join-Path $DEST_DIR "lib\ollama\runners"
+if (Test-Path $runnersDir) {
+    Get-ChildItem $runnersDir -Directory | Where-Object { $_.Name -like "cuda*" -or $_.Name -like "rocm*" } | ForEach-Object {
+        Remove-Item -Recurse -Force $_.FullName
+        Write-Host ("  pruned GPU runner: {0}" -f $_.Name) -ForegroundColor Yellow
+    }
+}
+
 Remove-Item -Recurse -Force $TEMP_DIR -ErrorAction SilentlyContinue
 Remove-Item -Force $TEMP_ZIP -ErrorAction SilentlyContinue