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/player/store.svelte.ts

@@ -505,6 +505,21 @@ export function removeFromQueue(idx: number): void {
   _error = null;
 }
 
+// Clear the whole queue and stop playback — mirrors removeFromQueue's
+// empty-queue branch. Also drops the radio/system source + self-heal closure
+// so the emptied player doesn't try to refill from a now-irrelevant source.
+export function clearQueue(): void {
+  _queue = [];
+  _index = 0;
+  _state = 'idle';
+  _position = 0;
+  _duration = 0;
+  _error = null;
+  _radioSeedId = null;
+  _queueSource = null;
+  _queueRefetch = null;
+}
+
 export function playFromQueueIndex(idx: number): void {
   if (idx < 0 || idx >= _queue.length) return;
   _radioSeedId = null;