feat(web): add shuffle, repeat, and audio-event reporting to player store

toggleShuffle (Fisher-Yates over queue[index+1..end] with injectable
RNG for test determinism), cycleRepeat (off → all → one → off),
reportStateFromAudio with full repeat-mode semantics on 'ended',
plus simple state mirroring for playing/paused/waiting/error. Extends
skipNext to wrap when repeat='all'.

web/src/lib/player/store.svelte.ts

@@ -79,8 +79,16 @@ export function skipNext(): void {
     _position = 0;
     _duration = 0;
     _state = 'loading';
+    return;
+  }
+  // At end of queue.
+  if (_repeat === 'all') {
+    _index = 0;
+    _position = 0;
+    _duration = 0;
+    _state = 'loading';
   } else {
-    // At end: no-repeat-aware logic yet (Task 2 extends this).
+    // 'off' or 'one' both pause at end on EXPLICIT skip.
     _state = 'paused';
     _position = _duration;
   }
@@ -118,3 +126,73 @@ export function reportTimeUpdate(sec: number): void {
 export function reportDuration(sec: number): void {
   _duration = Number.isFinite(sec) ? sec : 0;
 }
+
+// --- Shuffle (with injectable RNG for tests) ---
+
+let _rng: () => number = Math.random;
+export function __setShuffleRng(fn: () => number): void { _rng = fn; }
+
+export function toggleShuffle(): void {
+  _shuffle = !_shuffle;
+  if (_shuffle && _index + 1 < _queue.length) {
+    // Fisher-Yates shuffle over _queue[_index+1 .. end].
+    const arr = _queue.slice();
+    for (let j = arr.length - 1; j > _index; j--) {
+      const r = Math.floor(_rng() * (j - _index)) + _index + 1;
+      [arr[j], arr[r]] = [arr[r], arr[j]];
+    }
+    _queue = arr;
+  }
+}
+
+// --- Repeat ---
+
+export function cycleRepeat(): void {
+  _repeat = _repeat === 'off' ? 'all' : _repeat === 'all' ? 'one' : 'off';
+}
+
+export function reportStateFromAudio(
+  event: 'playing' | 'paused' | 'waiting' | 'ended' | 'error',
+  detail?: string
+): void {
+  switch (event) {
+    case 'playing':
+      _state = 'playing';
+      _error = null;
+      return;
+    case 'paused':
+      _state = 'paused';
+      return;
+    case 'waiting':
+      _state = 'loading';
+      return;
+    case 'error':
+      _state = 'error';
+      _error = detail ?? 'Playback failed.';
+      return;
+    case 'ended':
+      if (_repeat === 'one') {
+        _position = 0;
+        _state = 'loading';
+        if (_audioEl) _audioEl.currentTime = 0;
+        return;
+      }
+      if (_index + 1 < _queue.length) {
+        _index++;
+        _position = 0;
+        _duration = 0;
+        _state = 'loading';
+        return;
+      }
+      if (_repeat === 'all') {
+        _index = 0;
+        _position = 0;
+        _duration = 0;
+        _state = 'loading';
+      } else {
+        _state = 'paused';
+        _position = _duration;
+      }
+      return;
+  }
+}