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

changes/closed-pipe-crash.md

@@ -0,0 +1,4 @@
+type: fixed
+area: app
+
+- SubMiner no longer crashes with "write EPIPE" when the terminal command that started it is stopped with Ctrl+C.

changes/timing-review-thin-handles.md

@@ -0,0 +1,5 @@
+type: fixed
+area: overlay
+
+- Media timing review trim handles are now thin lines centered on the clip edge, so it's clear where the clip starts and ends and less of the waveform is covered.
+- Original subtitle boundaries use orange bars without text tags, leaving the waveform unobstructed.

changes/youtube-browser-window.md

@@ -0,0 +1,7 @@
+type: added
+area: youtube
+
+- Added a YouTube browser window (`subminer youtube`/`subminer yt`, or tray **Browse YouTube**) that keeps your YouTube login across restarts.
+- Clicking a video plays it in mpv instead of the page; middle-click, Shift/Ctrl-click, or the right-click menu queues it in mpv's playlist.
+- Queued YouTube videos get the same Japanese subtitle setup when mpv reaches them.
+- Closing the YouTube window quits a SubMiner started by `subminer youtube` (after mpv closes, if a video is still playing).

changes/youtube-translated-caption-429.md

@@ -0,0 +1,4 @@
+type: fixed
+area: youtube
+
+- YouTube Japanese subtitles no longer fail with "HTTP 429" on videos where YouTube also lists a machine-translated Japanese track; SubMiner now picks the real track and falls back to yt-dlp if a direct subtitle download is refused.

changes/youtube-whisper-subtitles.md

@@ -0,0 +1,7 @@
+type: added
+area: youtube
+
+- Added `youtube.subtitleSource`: set it to `whisper` to transcribe YouTube videos with Whisper instead of downloading YouTube's captions. The default stays `youtube`.
+- Whisper mode keeps the video paused while it transcribes, with progress in the subtitle generation modal; close the modal to keep watching, or cancel to continue without subtitles.
+- The subtitle generation modal (`Ctrl+Shift+G`) now also works on YouTube videos, whatever `youtube.subtitleSource` is set to.
+- Whisper mode downloads a small audio-only stream and deletes it once generation ends, or when you switch videos, close mpv, or quit.