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

launcher/config/cli-parser-builder.ts

@@ -29,6 +29,7 @@ export interface CliInvocations {
   jellyfinInvocation: JellyfinInvocation | null;
   configInvocation: CommandActionInvocation | null;
   settingsInvocation: CommandActionInvocation | null;
+  youtubeBrowserInvocation: CommandActionInvocation | null;
   mpvInvocation: CommandActionInvocation | null;
   appInvocation: { appArgs: string[] } | null;
   dictionaryTriggered: boolean;
@@ -123,6 +124,8 @@ function getTopLevelCommand(argv: string[]): { name: string; index: number } | n
     'doctor',
     'config',
     'settings',
+    'youtube',
+    'yt',
     'mpv',
     'logs',
     'dictionary',
@@ -177,6 +180,7 @@ export function parseCliPrograms(
   let jellyfinInvocation: JellyfinInvocation | null = null;
   let configInvocation: CommandActionInvocation | null = null;
   let settingsInvocation: CommandActionInvocation | null = null;
+  let youtubeBrowserInvocation: CommandActionInvocation | null = null;
   let mpvInvocation: CommandActionInvocation | null = null;
   let appInvocation: { appArgs: string[] } | null = null;
   let dictionaryTriggered = false;
@@ -514,6 +518,17 @@ export function parseCliPrograms(
       };
     });
 
+  commandProgram
+    .command('youtube')
+    .alias('yt')
+    .description('Open the YouTube browser (videos play in mpv)')
+    .option('--log-level <level>', 'Log level')
+    .action((options: Record<string, unknown>) => {
+      youtubeBrowserInvocation = {
+        logLevel: typeof options.logLevel === 'string' ? options.logLevel : undefined,
+      };
+    });
+
   commandProgram
     .command('mpv')
     .description('MPV helpers')
@@ -569,6 +584,7 @@ export function parseCliPrograms(
       jellyfinInvocation,
       configInvocation,
       settingsInvocation,
+      youtubeBrowserInvocation,
       mpvInvocation,
       appInvocation,
       dictionaryTriggered,