fix: piano roll tab không phát âm thanh - bỏ sessionBeatOffset để note phát theo item-relative khớp playhead (item ở vị trí != 0 trước đây schedule note ở now+startTime -> câm)

app/static/js/app.jsx

@@ -15705,15 +15705,13 @@ const App = () => {
     const synthEngine = track ? track.synth_engine : undefined;
     var allTracks = activeTracksRef.current || [];
     var mainCh = track ? assignTrackMidiChannel(track, allTracks) : 0;
-    // Compute session beat offset from target item
-    var sessionBeatOffset = 0;
-    var targetTrk = allTracks.find(function(t) { return t.id === st.trackId; });
-    if (targetTrk) {
-      var targetIt = (targetTrk.midiItems || []).find(function(m) { return m.id === st.target_id; });
-      if (targetIt) sessionBeatOffset = (targetIt.startTime / ((60.0 / bpmVal) * 4)) * 4;
-    }
+    // The piano-roll playhead (st.currentTime) and transport are item-relative:
+    // 0 = item start. Notes must be scheduled relative to the item too, otherwise
+    // items placed later in the project play `item.startTime` seconds in the
+    // future (silence when pressing play). Ghost notes are already relative to
+    // the item window, so no absolute-session offset is applied anywhere here.
     midiNotes.forEach(note => {
-      const noteOnBeat = (note.start_beat || 0) + sessionBeatOffset;
+      const noteOnBeat = note.start_beat || 0;
       const noteDurBeat = note.duration_beats || 1;
       const noteStartSec = noteOnBeat * secondsPerBeat;
       const noteDurSec = noteDurBeat * secondsPerBeat;
@@ -15737,7 +15735,7 @@ const App = () => {
       var ghostDest = getOrCreateTrackNode(ghostTrack, context);
       var ghostCh = ghostTrack ? assignTrackMidiChannel(ghostTrack, allTracks) : 0;
       layer.notes.forEach(function(note) {
-        var beat = (note.start_beat || 0) + sessionBeatOffset;
+        var beat = note.start_beat || 0;
         var dur = note.duration_beats || 1;
         var startSec = beat * secondsPerBeat;
         var durSec = dur * secondsPerBeat;