fix(web/m7-364): TrackRef field shape + seek-on-restore + drawer inert

CI svelte-check failed on 5 type errors caused by the slice using
duration_ms/album_name fields that don't exist on TrackRef (the real
shape uses duration_sec + album_id/album_title). Fixed across
QueueDrawer, QueueDrawer.test, QueueTrackRow.test, persisted.test,
and the inline `state.current = null` in PlayerBar.test (TrackRef |
undefined, not | null).

Final whole-slice review concerns also rolled in:

- C1 (Critical): persisted position was restored to UI but never
  seeked into the audio element — first timeupdate snapped _position
  back to 0. Added a one-shot _pendingRestorePosition module ref +
  consumePendingRestorePosition() export; layout's loadedmetadata
  handler now seeks once on restore.

- I1 (Important): throttled-write effect now wraps _queue / _index
  reads in untrack so the dependency tracking matches the design
  intent. Position remains the only tracked dep.

- I4 (Important): drawer gets inert={!queueDrawerOpen} so its inner
  buttons drop out of tab order when closed (aria-hidden alone
  doesn't do that). Removed redundant role="complementary" from
  <aside> (implied by the element). New test asserts inert binding.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/src/lib/components/QueueTrackRow.test.ts

@@ -16,11 +16,13 @@ vi.mock('$lib/player/store.svelte', () => ({
 const sampleTrack: TrackRef = {
   id: 't1',
   title: 'Song Title',
+  album_id: 'al1',
+  album_title: 'Album',
+  artist_id: 'ar1',
   artist_name: 'Artist Name',
-  album_name: 'Album',
-  duration_ms: 200000,
+  duration_sec: 200,
   stream_url: '/stream/t1'
-} as TrackRef;
+};
 
 describe('QueueTrackRow', () => {
   beforeEach(() => {