Restructure step 5: one media pipeline on a player host

- PlayerHost port (MediaKitHost): players by role, pins, hwdec policy,
  render probe, log routing, disposal order; the only media_kit user.
- MediaPipeline: plan (one pure switch over state, origin, caps,
  presence) -> resolve -> open (prepared player promoted, else fresh)
  -> ready; commands queued during a switch apply once (P15); viewers
  play the buffer and wait for a dropped source without seek loops (D6).
- Every web page resolved by our yt-dlp into an EDL with headers and
  cookies (danmaku excluded); mpv's ytdl_hook no longer used (ytdl=no).
- D11: sign-in errors say which cookies were used and whether they hold
  any for the site.
- Relay: 256 KiB slices read as they fill, superseded pulls released
  (seek-to-play ~4.2 s -> ~2.8 s, P29); own Jellyfin relay channel only
  when someone needs it (P28).
- STARSYNC_SMOKE run and a Windows CI smoke step after the build.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/desktop/lib/src/app/app_graph.dart

@@ -88,8 +88,8 @@ class AppGraph {
       prefs: () => AppSettings.instance.notifyPrefs,
     );
     final connection = Connection(notify: notifier.notify, identity: identity ?? ClientIdentity.stored());
-    final coordinator =
-        SessionCoordinator(notifier: notifier, connection: connection, ytDlp: p.links, jellyfin: jellyfin);
+    final coordinator = SessionCoordinator(
+        notifier: notifier, connection: connection, ytDlp: p.links, jellyfin: jellyfin, players: p.players);
     // Device-owned: the library box; AnimeFlow's runs when signed in.
     final matcher = library ??
         ShowMatcher(