feat(web): My Wave button, mood picker and endless wave playback (M4)

- WaveButton: TypeScript port of the prototype's canvas animation
  (orb and liquid), breathing at rest, pulsing to the track's BPM and
  energy in the cover palette, following the cursor, pressing with a
  spring; reduced motion and hidden tabs slow or stop it
- home: the wave in the centre with activity and mood chips; changing
  them while playing rebuilds the upcoming tracks without stopping
- player wave mode: asks for the next batch when two tracks are left,
  sends complete / skip / early skip / like / dislike as feedback and
  refreshes the queue right after a reaction or an early skip
- tracks expose bpm, energy and loudness once analysed; library page
  shows analysis progress and 7-day wave metrics; wave style setting

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/src/player.test.ts

@@ -14,6 +14,7 @@ const track = (id: string, duration_ms = 200_000): Track => ({
   available: true,
   stream_url: `/s/${id}`,
   reaction: null,
+  features: null,
 });
 
 const ids = (q: PlayQueue) => q.order.map((i) => q.tracks[i]!.id);
@@ -62,6 +63,23 @@ describe('PlayQueue', () => {
   });
 });
 
+describe('PlayQueue in the wave', () => {
+  it('appends batches and drops upcoming tracks', () => {
+    const q = new PlayQueue();
+    q.set([track('a'), track('b'), track('c')]);
+    q.next();
+    expect(q.remaining).toBe(1);
+    q.append([track('d'), track('e')]);
+    expect(q.remaining).toBe(3);
+    q.dropUpcoming();
+    expect(q.current?.id).toBe('b');
+    expect(q.remaining).toBe(0);
+    expect(q.tracks.map((t) => t.id)).toEqual(['a', 'b']);
+    q.append([track('x')]);
+    expect(q.next()?.id).toBe('x');
+  });
+});
+
 describe('PlayAttempt', () => {
   it('counts only time actually played', () => {
     const a = new PlayAttempt(track('a'));