fix: resolve additional bugs identified in code review

- core: remove DispatchGroup from MediaExtractionEngine to fix hanging on yt-dlp launch failure
- core: clear readabilityHandlers in Aria2DownloadEngine if process fails to launch
- core: fix TOCTOU type warning for findFreePort
- build: fix inverted logic in Mach-O validation script
- ci: fix hardcoded macOS SDK version check in release workflow
- ci: prevent workflow_dispatch from failing on verify-tag

.github/workflows/release.yml

@@ -17,7 +17,7 @@ permissions:
 jobs:
   macos-arm64-dmg:
     name: Build macOS ARM64 DMG
-    runs-on: macos-26
+    runs-on: macos-14
 
     steps:
       - name: Check out repository
@@ -49,14 +49,14 @@ jobs:
           xcode-select -p
           xcrun --sdk macosx --show-sdk-version
 
-      - name: Verify macOS 26 SDK
+      - name: Verify macOS 14+ SDK
         shell: bash
         run: |
           SDK_VERSION="$(xcrun --sdk macosx --show-sdk-version)"
           SDK_MAJOR="${SDK_VERSION%%.*}"
 
-          if [[ "$SDK_MAJOR" != "26" ]]; then
-            echo "Expected macOS 26 SDK, got macOS $SDK_VERSION" >&2
+          if [[ "$SDK_MAJOR" -lt 14 ]]; then
+            echo "Expected at least macOS 14 SDK, got macOS $SDK_VERSION" >&2
             exit 1
           fi
 
@@ -123,5 +123,9 @@ jobs:
             gh release upload "$TAG_NAME" dist/*.dmg --clobber
             gh release edit "$TAG_NAME" --notes-file release_notes.md
           else
-            gh release create "$TAG_NAME" dist/*.dmg --title "$TAG_NAME" --notes-file release_notes.md --verify-tag
+            if [[ "${{ github.event_name }}" == "workflow_dispatch" ]]; then
+              gh release create "$TAG_NAME" dist/*.dmg --title "$TAG_NAME" --notes-file release_notes.md
+            else
+              gh release create "$TAG_NAME" dist/*.dmg --title "$TAG_NAME" --notes-file release_notes.md --verify-tag
+            fi
           fi