feat(youtube): add YouTube browser window and Whisper subtitle source

- Add `subminer youtube`/`yt` and tray "Browse YouTube" window that plays or queues picked videos in mpv
- Add `youtube.subtitleSource` (`youtube` | `whisper`) to transcribe YouTube audio via subtitle generation
- Allow the subtitle generation modal on YouTube videos
- Pick the real Japanese track over machine-translated ones and fall back to yt-dlp on HTTP 429
- Remove legacy launcher youtubeSubgen/whisper/AI args and `--youtube-mode`
- Fix EPIPE crash when the launching terminal is closed with Ctrl+C
- Thin media timing review handles with orange original-boundary bars
- Update docs and change fragments

src/main/cli-runtime.ts

@@ -52,6 +52,7 @@ export interface CliCommandRuntimeServiceContext {
   openHachidoriSettings: () => void;
   openConfigSettingsWindow: () => void;
   openSyncUiWindow: () => void;
+  openYoutubeBrowserWindow: () => void;
   cycleSecondarySubMode: () => void;
   openRuntimeOptionsPalette: () => void;
   printHelp: () => void;
@@ -139,6 +140,7 @@ function createCliCommandDepsFromContext(
       openHachidoriSettings: context.openHachidoriSettings,
       openConfigSettingsWindow: context.openConfigSettingsWindow,
       openSyncUiWindow: context.openSyncUiWindow,
+      openYoutubeBrowserWindow: context.openYoutubeBrowserWindow,
       cycleSecondarySubMode: context.cycleSecondarySubMode,
       openRuntimeOptionsPalette: context.openRuntimeOptionsPalette,
       printHelp: context.printHelp,