feat(anime): filter episodes and mark them watched by hand

- Add a filter box above the episode list for a number, range, or name substring, with a "N of M" counter
- Read watch marks from the immersion tracker stats and show them per episode, with a watched count in the header, refreshed on window focus
- Add a right-click menu to mark one episode or a whole catch-up span (this and everything below) watched/unwatched
- Add setWatched/getWatchState IPC plumbing so a manual mark creates the stats row for an episode that was never played

src/main.ts

@@ -3332,6 +3332,16 @@ const animeBrowserRuntime = createAnimeBrowserRuntime({
   },
   showMpvOsd: (text) =>
     overlayNotificationsRuntime.showConfiguredStatusNotification(text, { title: 'Anime' }),
+  getWatchState: async (statsPaths) => {
+    // Browsing can precede any playback, so the tracker may not be up yet; it
+    // is the same instance playback records into once it is.
+    ensureImmersionTrackerStarted();
+    return (await appState.immersionTracker?.getStreamWatchState(statsPaths)) ?? new Map();
+  },
+  setWatchState: async (episodes, watched) => {
+    ensureImmersionTrackerStarted();
+    return (await appState.immersionTracker?.setStreamWatchState(episodes, watched)) ?? 0;
+  },
   onPlaybackMetadata: (metadata) => {
     streamPlaybackMetadata.set(metadata);
     // Set before mpv reports the path change, so the session that change starts