feat: Snap to Scale toggle + remove tool buttons + no menu on erase sweep

- Added snapToScale state + toggle switch in piano roll toolbar
- snapPitchToScale only applies when snapToScale is true
- Removed Select/Pen/Eraser tool buttons
- Right-click drag erase sweep sets swallowContextMenuRef=true
  so context menu won't appear during sweep

app/static/js/app.jsx

@@ -5068,12 +5068,12 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
         mode: 'draw',
         idx: -1,
         startOffsetBeat: start,
-        startOffsetPitch: snapPitchToScale(pitch, selectedScale),
+        startOffsetPitch: snapToScale ? snapPitchToScale(pitch, selectedScale) : pitch,
         drawNoteId: noteId,
         drawDuration: initialDur,
-        visitedPitches: [snapPitchToScale(pitch, selectedScale)],
+        visitedPitches: snapToScale ? [snapPitchToScale(pitch, selectedScale)] : [pitch],
         initialBeat: start,
-        initialPitch: snapPitchToScale(pitch, selectedScale)
+        initialPitch: snapToScale ? snapPitchToScale(pitch, selectedScale) : pitch
       });
       // Play the note with SoundFont
       if (window.SonicSF) {
@@ -5118,6 +5118,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     const rc = rightClickDragRef.current;
     if (rc.active && (Math.abs(e.clientX - rc.startX) > 5 || Math.abs(e.clientY - rc.startY) > 5)) {
       rc.active = false;
+      swallowContextMenuRef.current = true;
       notesBeforeDragRef.current = JSON.parse(JSON.stringify(notes));
       setDraggedNote({ mode: 'erase_sweep', visitedPitches: [] });
       return;
@@ -5155,7 +5156,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
           return { ...n, duration_beats: newDur };
         }));
       }
-      const snappedPitch = snapPitchToScale(pitch, selectedScale);
+      const snappedPitch = snapToScale ? snapPitchToScale(pitch, selectedScale) : pitch;
       if (!visited.includes(snappedPitch)) {
         const newPitches = [...visited, snappedPitch];
         const totalSpan = Math.max(0.125, beat - draggedNote.initialBeat);
@@ -5461,6 +5462,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     }
   };
   const [selectedScale, setSelectedScale] = React.useState(null);
+  const [snapToScale, setSnapToScale] = React.useState(true);
   const [scaleMenuPos, setScaleMenuPos] = React.useState(null);
   const scaleMenuOriginRef = React.useRef(null);
   const [aiPrompt, setAiPrompt] = React.useState('');
@@ -5616,12 +5618,16 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
     "data-lucide": "music",
     className: "w-3.5 h-3.5"
   }), st.label), /*#__PURE__*/React.createElement("div", {
-    className: "flex bg-zinc-800 p-0.5 rounded border border-zinc-700 text-xs"
-  }, ['select', 'pen', 'eraser'].map(tool => /*#__PURE__*/React.createElement("button", {
-    key: tool,
-    onClick: () => setActiveRollTool(tool),
-    className: `px-2.5 py-1 rounded capitalize ${activeRollTool === tool ? 'bg-yellow-600 text-white font-bold' : 'text-zinc-400 hover:text-zinc-200'}`
-  }, tool))), /*#__PURE__*/React.createElement("div", {
+    className: "flex items-center gap-1 text-xs"
+  }, /*#__PURE__*/React.createElement("span", {
+    className: "text-zinc-500 font-semibold"
+  }, "Snap to Scale"), /*#__PURE__*/React.createElement("button", {
+    onClick: () => setSnapToScale(!snapToScale),
+    className: `w-7 h-4 rounded-full transition-colors relative ${snapToScale ? 'bg-yellow-600' : 'bg-zinc-700'}`,
+    style: { padding: 0 }
+  }, /*#__PURE__*/React.createElement("div", {
+    className: `w-3 h-3 rounded-full bg-white absolute top-0.5 transition-transform ${snapToScale ? 'translate-x-3.5' : 'translate-x-0.5'}`
+  }))), /*#__PURE__*/React.createElement("div", {
     className: "flex items-center gap-1 text-xs"
   }, /*#__PURE__*/React.createElement("span", {
     className: "text-zinc-500 font-semibold"