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/config/definitions.ts

@@ -51,7 +51,6 @@ const {
   jellyfin,
   discordPresence,
   ai,
-  youtubeSubgen,
 } = INTEGRATIONS_DEFAULT_CONFIG;
 const { subtitleStyle, subtitleSidebar } = SUBTITLE_DEFAULT_CONFIG;
 const { immersionTracking } = IMMERSION_DEFAULT_CONFIG;
@@ -89,7 +88,6 @@ export const DEFAULT_CONFIG: ResolvedConfig = {
   jellyfin,
   discordPresence,
   ai,
-  youtubeSubgen,
   immersionTracking,
   stats,
 };