fix: skip st.notes sync when draggedNote active (prevents brush flicker)

app/static/js/app.jsx

@@ -4572,6 +4572,8 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
   const noteMaxBeat = (st.notes || []).reduce((max, n) => Math.max(max, (n.start_beat || 0) + (n.duration_beats || 1)), 0);
   const [selectionMarquee, setSelectionMarquee] = React.useState(null); // { startBeat, startPitch, currentBeat, currentPitch }
   const [draggedNote, setDraggedNote] = React.useState(null); // { mode: 'move'|'resize', idx, startOffsetBeat, originalStart }
+  const draggedNoteRef = React.useRef(draggedNote);
+  draggedNoteRef.current = draggedNote;
   const [hoveredResizeIdx, setHoveredResizeIdx] = React.useState(-1);
   const [rollBeats, setRollBeats] = React.useState(Math.max(noteMaxBeat + 16, 64));
   const rollBeatsRef = React.useRef(rollBeats);
@@ -4585,7 +4587,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
   const [notes, setNotes] = React.useState(st.notes || []);
   const notesRef = React.useRef(notes);
   notesRef.current = notes;
-  React.useEffect(() => { setNotes(st.notes || []); }, [st.notes]);
+  React.useEffect(() => { if (!draggedNoteRef.current) setNotes(st.notes || []); }, [st.notes]);
   const brushVelocityRef = React.useRef(0.8);
   const [selectedNoteIds, setSelectedNoteIds] = React.useState([]);
   React.useEffect(() => {