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/renderer/modals/subtitle-generation.ts

@@ -88,7 +88,7 @@ export function createSubtitleGenerationModal(
     const vad = snapshot ? describeGenerationVad(snapshot.vad) : null;
     const tools = snapshot ? describeGenerationTools(snapshot.tools) : null;
     const readyMessage = !snapshot?.mediaPath
-      ? 'Open a local file or a YouTube video to generate subtitles.'
+      ? 'Open a local file, a Jellyfin stream, or a YouTube video to generate subtitles.'
       : !tools?.ready
         ? 'Install the missing tools or set their paths in Settings, then click Check again.'
         : !model?.ready
@@ -97,7 +97,8 @@ export function createSubtitleGenerationModal(
             ? 'Download the speech detection model or uncheck Focus on spoken dialogue.'
             : 'Ready when you are.';
     dom.media.textContent =
-      snapshot?.mediaPath ?? 'Open a local file or a YouTube video in the player first.';
+      snapshot?.mediaPath ??
+      'Open a local file, a Jellyfin stream, or a YouTube video in the player first.';
     dom.tools.textContent = tools?.text ?? 'Checking local tools...';
     dom.model.textContent = model?.text ?? 'Checking local models...';
     dom.modelPicker.classList.toggle('hidden', !snapshot || Boolean(snapshot.externalModelPath));