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/QueueDrawer.test.ts

@@ -25,11 +25,13 @@ vi.mock('$lib/player/store.svelte', () => ({
 const t = (id: string): TrackRef => ({
   id,
   title: `Song ${id}`,
+  album_id: `al-${id}`,
+  album_title: 'A',
+  artist_id: `ar-${id}`,
   artist_name: `Artist ${id}`,
-  album_name: 'A',
-  duration_ms: 200000,
+  duration_sec: 200,
   stream_url: `/stream/${id}`
-} as TrackRef);
+});
 
 describe('QueueDrawer', () => {
   beforeEach(() => {
@@ -77,7 +79,16 @@ describe('QueueDrawer', () => {
     openValue = false;
     queueValue = [t('a')];
     render(QueueDrawer);
-    const aside = screen.getByRole('complementary', { hidden: true });
+    const aside = screen.getByLabelText(/playback queue/i, { hidden: true });
     expect(aside).toHaveAttribute('aria-hidden', 'true');
   });
+
+  it('drawer has inert attribute when closed', () => {
+    openValue = false;
+    queueValue = [t('a')];
+    render(QueueDrawer);
+    const aside = document.querySelector('aside[aria-label="Playback queue"]');
+    expect(aside).not.toBeNull();
+    expect(aside!.hasAttribute('inert')).toBe(true);
+  });
 });