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

docs-site/subtitle-generation.md

@@ -10,11 +10,13 @@ When a video has no Japanese subtitles, SubMiner can transcribe its audio into a
 
 Downloaded models go to `models/whisper/` next to your SubMiner config file. A configured `modelPath` always wins over the modal's choice.
 
+YouTube videos can use the same setup automatically in place of YouTube's captions. See [Generate subtitles with Whisper](/youtube-integration#generate-subtitles-with-whisper).
+
 The modal's **Local tools** section lists anything missing. After you install a tool or change a path, click **Check again**.
 
 ## Generating from the overlay
 
-1. Open a local video in mpv and select its Japanese audio track.
+1. Open a local video in mpv and select its Japanese audio track, or play a YouTube video.
 2. Press `Ctrl+Shift+G`. If the subtitle sidebar is empty, its **Generate Japanese subtitles** button opens the same modal.
 3. Pick a model and download it if needed.
 4. Optionally check **Focus on spoken dialogue** (see below).
@@ -24,6 +26,8 @@ The modal shows progress. **Cancel** stops the job. Closing the modal lets the j
 
 SubMiner saves `<video>.ja.generated.srt` next to the video and adds a number if that name is taken. If the same file is still playing, it loads the subtitles and resets the subtitle delay.
 
+For a YouTube video, SubMiner downloads its audio first and pauses the video until the subtitles load. The subtitles are temporary, and the audio is deleted when generation ends or you switch videos. See [YouTube integration](/youtube-integration#generate-subtitles-with-whisper).
+
 Change the shortcut with `shortcuts.openSubtitleGeneration`.
 
 ## Generating from the launcher