feat(subtitles): generate Japanese subtitles during Jellyfin playback (#294)

* feat(subtitles): generate Japanese subtitles during Jellyfin playback

- Read the item's original file via toJellyfinOriginalStreamUrl and write output to a temp dir
- Transcoded playback uses Jellyfin's audio index and only external references
- Show Jellyfin media by title and redact URL tokens in subprocess errors
- Update overlay copy, docs, and changelog fragment

* fix(subtitles): redact full stream tokens and reuse one Jellyfin output folder

* test(subtitles): make Jellyfin output path assertions platform-neutral

- Compare dirname/basename via node:path instead of POSIX-only regexes
- Assert the full sub-add command uses the generated output path

docs-site/jellyfin-integration.md

@@ -23,6 +23,8 @@ SubMiner starts mpv if it is not already running. Pause, seek, stop, and track c
 
 SubMiner selects a Japanese subtitle track automatically and resets mpv's subtitle delay to zero. It direct-plays files when it can and asks Jellyfin to transcode the rest.
 
+If an episode has no Japanese subtitles, you can [generate them with Whisper](/subtitle-generation#generating-from-the-overlay) while it plays.
+
 On Windows, casting finds mpv through `mpv.executablePath`, then `SUBMINER_MPV_PATH`, then `PATH`. An invalid `mpv.executablePath` stops mpv from starting.
 
 ## Playing from the terminal

docs-site/subtitle-generation.md

@@ -16,7 +16,7 @@ The modal's **Local tools** section lists anything missing. After you install a
 
 ## Generating from the overlay
 
-1. Open a local video in mpv and select its Japanese audio track, or play a YouTube video.
+1. Open a local video in mpv and select its Japanese audio track, or play a Jellyfin or 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).
@@ -26,6 +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 Jellyfin video, SubMiner reads the original file from your server and saves the subtitles to `~/.cache/subminer/generated-subs/`, since a stream has no folder of its own. Each Jellyfin generation replaces the previous file there. Playback keeps going while it works. If Jellyfin is transcoding, SubMiner transcribes the audio track that playback started with.
+
 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`.
@@ -46,7 +48,7 @@ subminer generate-subs episode.mkv --model-path /path/to/ggml-small.bin
 | `--audio-stream <index>` | Pick an audio stream by its absolute FFmpeg index             |
 | `--output <path>`        | Write to this SRT path. Existing files are never overwritten. |
 
-With a file argument, SubMiner uses the audio stream tagged Japanese, or the first stream. `Ctrl+C` cancels.
+With a file argument, SubMiner uses the audio stream tagged Japanese, or the first stream. `Ctrl+C` cancels. The launcher only works with local files. Use the overlay for Jellyfin and YouTube.
 
 ## Choosing a model