fix: force piano roll grid redraw on snap change via renderTick

snapVal already in useLayoutEffect deps. Added renderTick
counter bumped in onChange to guarantee canvas redraw.

app/static/js/app.jsx

@@ -5795,6 +5795,7 @@ Ví dụ: Nhạc phim epic, dàn nhạc giao hưởng, tempo 130 BPM, giọng Cm
 const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, activeTracks, onClose, onUpdateNotes, onSaveNotes, setSubTabs, onPlayPause, onStop, isPlaying, playPreviewNote, showToast, midiDevices, recordingState, recTempMidiNotes, onRecord, selectedMidiInputId, onMidiInputSelect, activeMidiPitches, onInstrumentSelect, onRescheduleMidi, onSeekPlayhead }) => {
   const [activeRollTool, setActiveRollTool] = React.useState('select');
   const [snapVal, setSnapVal] = React.useState('1');
+  const [renderTick, setRenderTick] = React.useState(0);
   const [ccMode, setCcMode] = React.useState('velocity');
   const [rollZoom, setRollZoom] = React.useState(60); // local horizontal zoom factor
   const [aiBarStart, setAiBarStart] = React.useState(0);
@@ -6265,7 +6266,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, activeTracks, onClos
         ctx.stroke();
       }
     }
-  }, [notes, snapVal, rollZoom, selectedNoteIds, selectionMarquee, st.currentTime, bpm, viewWidth, viewBeats, recordingState, recTempMidiNotes, showGhostNotes, sessionSyncMode, ghostLayers, renderBeatOffset]);
+  }, [notes, snapVal, rollZoom, selectedNoteIds, selectionMarquee, st.currentTime, bpm, viewWidth, viewBeats, recordingState, recTempMidiNotes, showGhostNotes, sessionSyncMode, ghostLayers, renderBeatOffset, renderTick]);
 
   React.useLayoutEffect(() => {
     const canvas = ccCanvasRef.current;
@@ -7199,7 +7200,7 @@ const beatSec = 60.0 / (parseInt(bpm) || 120);
       className: "text-zinc-500 font-semibold"
     }, "Snap:"), React.createElement("select", {
       value: snapVal,
-      onChange: e => setSnapVal(e.target.value),
+      onChange: e => { setSnapVal(e.target.value); setRenderTick(t => t + 1); },
       className: "bg-zinc-800 border border-zinc-700 text-zinc-300 rounded px-1.5 py-0.5 outline-none focus:border-yellow-500"
     }, ['free', '4', '1', '1/2', '1/4', '1/8', '1/16', '1/32'].map(v => React.createElement("option", {
       key: v,