fix(player): keep seekbar waveform on current track during gapless preload

Byte-preload for the next track called refreshWaveformForTrack(next), which
writes global waveformBins and replaced the playing track’s waveform when
seeking near the end. Drop that call and ignore stale RPC results if
currentTrack changed while the fetch was in flight.

src/store/playerStore.ts

@@ -678,6 +678,8 @@ async function refreshWaveformForTrack(trackId: string) {
   if (!trackId) return;
   try {
     const row = await invoke<WaveformCachePayload | null>('analysis_get_waveform_for_track', { trackId });
+    // Never apply bins for a non-current track (e.g. gapless byte-preload fetches the neighbour).
+    if (usePlayerStore.getState().currentTrack?.id !== trackId) return;
     const bins = row ? coerceWaveformBins(row.bins) : null;
     if (!bins || bins.length === 0) {
       usePlayerStore.setState({
@@ -945,8 +947,8 @@ function handleAudioProgress(current_time: number, duration: number) {
     // Byte pre-download — runs early so bytes are cached by chain time.
     if ((shouldBytePreload || shouldBytePreloadForGaplessBackup) && nextTrack.id !== bytePreloadingId) {
       bytePreloadingId = nextTrack.id;
-      // Keep analysis context warm for the upcoming track before any source swap.
-      void refreshWaveformForTrack(nextTrack.id);
+      // Loudness cache only — do not call refreshWaveformForTrack(next): it writes global
+      // waveformBins and would replace the current track's seekbar while still playing it.
       void refreshLoudnessForTrack(nextTrack.id, { syncPlayingEngine: false });
       if (import.meta.env.DEV) {
         console.info('[psysonic][preload-request]', {