feat(youtube): add YouTube browser window and Whisper subtitle source (#273)

docs-site/youtube-integration.md

@@ -24,6 +24,41 @@ SubMiner picks tracks in this order. Manual (uploaded) tracks win over auto-gene
 
 Press `Ctrl+Alt+C` during playback to open the subtitle picker. It lists every track with its language and kind, and lets you choose different primary and secondary tracks or retry a failed load.
 
+## Generate subtitles with Whisper
+
+SubMiner can transcribe a YouTube video's audio on your computer. For one video, press `Ctrl+Shift+G` and click **Generate subtitles**. To always use Whisper instead of YouTube's captions, set `youtube.subtitleSource` to `whisper`, or choose **Generate with Whisper** under **Settings > Behavior > YouTube Playback Settings**. The change applies to the next video.
+
+```jsonc
+{
+  "youtube": { "subtitleSource": "whisper" },
+}
+```
+
+Whisper uses the model and tools from [Japanese subtitle generation](/subtitle-generation), so set those up first.
+
+- The video stays paused while the subtitles are generated, and the subtitle generation modal shows the progress. Close the modal to keep watching while generation continues. **Cancel** stops it and resumes the video without subtitles.
+- The subtitles load and playback resumes as soon as they are ready.
+- SubMiner downloads the smallest audio stream of at least 48 kbps, in the video's original language, never an auto-dub.
+- The audio is deleted as soon as generation finishes or fails, and when you switch to another video, close mpv, or quit SubMiner. Switching videos also stops the generation.
+- No secondary subtitles load. The picker (`Ctrl+Alt+C`) still loads YouTube tracks by hand.
+
+## Browse YouTube in SubMiner
+
+Open a YouTube window with `subminer youtube` (or `subminer yt`), or from the tray (**Browse YouTube**). Sign in once and the login is kept across restarts. Videos you pick play in mpv with the same subtitle setup as above, and SubMiner starts mpv if it is not running.
+
+When SubMiner was started by `subminer youtube`, closing the window quits it. If a video is still playing, SubMiner quits when you close mpv instead.
+
+| Action                                                       | Result                              |
+| ------------------------------------------------------------ | ----------------------------------- |
+| Click a video                                                | Play it now                         |
+| Middle-click, or `Shift`/`Ctrl`+click                        | Add it to the end of mpv's playlist |
+| Right-click a video                                          | **Play in mpv** or **Queue in mpv** |
+| `Alt+Left` / `Alt+Right`, mouse back/forward, or right-click | Go back or forward                  |
+
+Queued videos get their subtitles loaded when mpv reaches them. Open the queue with the playlist browser (`Ctrl+Alt+P`) to reorder or skip entries.
+
+If Google refuses the sign-in, try again once. The window uses a standard Chrome user agent, but Google can still block embedded browsers.
+
 ## Secondary subtitle languages
 
 YouTube secondary selection is fixed to English. `secondarySub.secondarySubLanguages` and `secondarySub.autoLoadSecondarySub` apply only to local files and Jellyfin. `secondarySub.defaultMode` still controls how the secondary bar is shown. Use the picker to load a different secondary language.
@@ -56,6 +91,8 @@ See [Configuration](/configuration#youtube-playback-settings) for all `youtube`
 
 **Poor subtitle quality.** Auto-generated captions are often inaccurate. SubMiner uses a manual track when one exists.
 
+**Subtitles fail with HTTP 429.** YouTube is refusing caption requests from your network. It can last hours or days, and waiting or signing in does not always help. [Generate them with Whisper](#generate-subtitles-with-whisper) instead.
+
 A missing or failed secondary track never blocks playback.
 
 ## Stats