fix(jellyfin): fix discovery loop, device identity, tray state, and Disc

- Derive device identity from OS hostname; remove legacy configurable client/device fields
- Prevent discovery playback from reloading active item, misreporting pause state, and duplicate overlay restores
- Restart stale tray discovery sessions without re-login when server drops SubMiner cast target
- Sync tray discovery checkbox state on Linux after CLI/startup/remote-session changes
- Stop Discord presence falling back to stream URLs; prime title before tokenized stream loads
- Fix picker library discovery when log level is above info
- Fix config.example.jsonc trailing commas and array formatting

src/main/runtime/jellyfin-subtitle-cache-io.ts

@@ -0,0 +1,73 @@
+import * as path from 'path';
+
+type JellyfinSubtitleCacheTrack = {
+  index: number;
+  deliveryUrl?: string | null;
+};
+
+type JellyfinSubtitleCacheEntry = {
+  path: string;
+  cleanupDir: string;
+};
+
+type FetchResponseLike = {
+  ok: boolean;
+  status: number;
+  arrayBuffer: () => Promise<ArrayBuffer>;
+};
+
+type JellyfinSubtitleCacheIoDeps = {
+  tmpDir: () => string;
+  makeTempDir: (prefix: string) => Promise<string>;
+  writeFile: (filePath: string, bytes: Uint8Array) => Promise<void>;
+  removeDir: (dir: string, options: { recursive: true; force: true }) => void;
+  fetch: (url: string) => Promise<FetchResponseLike>;
+};
+
+function getSubtitleExtension(deliveryUrl: string): string {
+  const urlPath = (() => {
+    try {
+      return new URL(deliveryUrl).pathname;
+    } catch {
+      return deliveryUrl;
+    }
+  })();
+  return path.extname(urlPath).slice(0, 16) || '.srt';
+}
+
+export function createJellyfinSubtitleCacheIo(deps: JellyfinSubtitleCacheIoDeps) {
+  return {
+    async cacheSubtitleTrack(
+      track: JellyfinSubtitleCacheTrack,
+    ): Promise<JellyfinSubtitleCacheEntry> {
+      if (!track.deliveryUrl) {
+        throw new Error('Jellyfin subtitle track has no delivery URL');
+      }
+
+      const cacheDir = await deps.makeTempDir(
+        path.join(deps.tmpDir(), 'subminer-jellyfin-subtitles-'),
+      );
+      const subtitlePath = path.join(
+        cacheDir,
+        `track-${track.index}${getSubtitleExtension(track.deliveryUrl)}`,
+      );
+      try {
+        const response = await deps.fetch(track.deliveryUrl);
+        if (!response.ok) {
+          throw new Error(`Failed to download Jellyfin subtitle (HTTP ${response.status})`);
+        }
+        const bytes = new Uint8Array(await response.arrayBuffer());
+        await deps.writeFile(subtitlePath, bytes);
+      } catch (error) {
+        deps.removeDir(cacheDir, { recursive: true, force: true });
+        throw error;
+      }
+      return { path: subtitlePath, cleanupDir: cacheDir };
+    },
+    cleanupCachedSubtitles(dirs: string[]): void {
+      for (const dir of dirs) {
+        deps.removeDir(dir, { recursive: true, force: true });
+      }
+    },
+  };
+}