refactor(queue): co-locate QueuePanel UI into features/queue

Extract the queue UI (QueuePanel + queuePanel/* components + useQueue* hooks)
into features/queue/ with a barrel. This is the chosen playback/queue boundary:
queue = the QueuePanel UI that CONSUMES the playback store; queue STATE and the
audio engine stay in store/ (playback-core, moved separately). Verified
one-way: no playback-core file imports the queue UI back (only doc comments
mention it).

Excluded as NOT queue-UI: useIdlePlayQueuePull (AppShell) and
usePlayQueueSyncLedState (ConnectionIndicator) are queue-SYNC orchestration,
not panel UI — left in hooks/ to move with playback.

Pure move. One test fix: QueuePanel.test.tsx reads its subject via a hardcoded
readFileSync('src/components/QueuePanel.tsx') path (architecture-pin grep for
forbidden HTML5 DnD) — repointed to the new location (the move tool can't
rewrite non-import string paths). tsc 0, lint 0/0, suite 319/2353 green.

src/features/queue/hooks/useQueueTracks.ts

@@ -0,0 +1,38 @@
+import { useMemo, useSyncExternalStore } from 'react';
+import { usePlayerStore } from '@/store/playerStore';
+import type { QueueItemRef, Track } from '@/store/playerStoreTypes';
+import { resolveQueueTrack } from '@/utils/library/queueTrackView';
+import {
+  getQueueResolverVersion,
+  subscribeQueueResolver,
+} from '@/utils/library/queueTrackResolver';
+
+/**
+ * Stable queue selectors (queue thin-state). The store is refs-canonical now:
+ * full `Track`s come from the resolver cache (placeholder until a fetch lands),
+ * with session star/rating overrides (F4) merged on read via resolveQueueTrack.
+ */
+
+/** The track at a queue index, or null. */
+export function useQueueTrackAt(idx: number): Track | null {
+  const ref = usePlayerStore(s => s.queueItems[idx] ?? null);
+  const starredOverrides = usePlayerStore(s => s.starredOverrides);
+  const userRatingOverrides = usePlayerStore(s => s.userRatingOverrides);
+  const version = useSyncExternalStore(subscribeQueueResolver, getQueueResolverVersion);
+  return useMemo(() => {
+    if (!ref) return null;
+    return resolveQueueTrack(ref);
+  // version drives re-resolution as the cache fills; overrides drive the merge.
+  // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [ref, starredOverrides, userRatingOverrides, version]);
+}
+
+/** The currently playing track, or null. */
+export function useCurrentTrack(): Track | null {
+  return usePlayerStore(s => s.currentTrack);
+}
+
+/** The whole queue as thin refs (the canonical list). */
+export function useQueueItems(): QueueItemRef[] {
+  return usePlayerStore(s => s.queueItems);
+}