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

src/core/services/index.ts

@@ -130,6 +130,7 @@ export {
   listSubtitleTracks as listJellyfinSubtitleTracksRuntime,
   resolvePlaybackPlan as resolveJellyfinPlaybackPlanRuntime,
   ticksToSeconds as jellyfinTicksToSecondsRuntime,
+  toJellyfinOriginalStreamUrl,
 } from './jellyfin';
 export { JellyfinRemoteSessionService } from './jellyfin-remote';
 export {