feat(anime): queue episodes to play next across anime

- Episode rows gain Play/Queue actions (and matching context-menu items); queued rows show their place in line, with a queue count and Clear queue in the episode header
- Queue lives in the main process (`anime-browser-queue.ts`) so it survives the browser window closing and advances on mpv's end-file even when nobody is watching; streams resolve at play time so a signed URL cannot expire while queued
- Holds mpv's keep-open off while the queue waits and restores it once empty; queueing with nothing playing just plays immediately
- Adds anime-browser-queue and episode-queue unit tests, IPC channels/contracts, and doc updates

docs/architecture/domains.md

@@ -30,7 +30,9 @@ Read when: you need to find the owner module for a behavior or test surface
 - Anime browser: extension bridge client, sidecar, and stream handling in `src/anime-bridge/`;
   browser window UI in `src/animeui/` (preload `src/preload-animeui.ts`); runtime wiring in
   `src/main/runtime/anime-browser-runtime.ts`, `src/main/runtime/anime-browser-ipc-handlers.ts`,
-  `src/main/runtime/anime-bridge-installer.ts`, `src/main/runtime/stream-playback-metadata.ts`
+  `src/main/runtime/anime-bridge-installer.ts`, `src/main/runtime/stream-playback-metadata.ts`.
+  The play queue is app-level rather than an mpv playlist (`src/main/runtime/anime-browser-queue.ts`):
+  a queued episode is resolved when its turn comes, driven off mpv's `end-file`
 - Window trackers: `src/window-trackers/`
 - Stats HTTP app: `src/core/services/stats-server.ts`, with route groups and shared route support
   in `src/core/services/stats-server/`