feat(player): web queue auto-follow + jump-to-current pill + clear-queue — #1944

QueueList now follows the now-playing row as the track auto-advances (only
while it's in view), centers it on open, and surfaces a 'Jump to current' pill
once the user scrolls it off-screen. Header gains a clear-queue action backed
by a new store clearQueue() that empties the queue and stops playback.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

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

@@ -25,10 +25,12 @@ vi.mock('$lib/player/store.svelte', () => ({
     get queueDrawerOpen() { return openValue; }
   },
   // QueueTrackRow imports these from the store; provide stubs so its
-  // module-load doesn't break when QueueDrawer renders rows.
+  // module-load doesn't break when QueueDrawer renders rows. QueueList
+  // imports clearQueue for its header action.
   playFromQueueIndex: vi.fn(),
   removeFromQueue: vi.fn(),
-  moveQueueItem: vi.fn()
+  moveQueueItem: vi.fn(),
+  clearQueue: vi.fn()
 }));
 
 import QueueDrawer from './QueueDrawer.svelte';