fix: scale menu on grid canvas, not keybed; erase sweep removed

- Context menu (Scales) appears at right-click position on grid canvas
- Removed erase sweep on right-click (blocked brush after menu close)
- Removed keybed onContextMenu (was wrong position)
- Store menu origin ref so sub-menus don't drift on hover

app/static/js/app.jsx

@@ -4912,7 +4912,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
 
     if (scaleMenuPos) setScaleMenuPos(null);
 
-    // Right click -> Quick delete note or start erase sweep
+    // Right click -> Quick delete note
     if (e.button === 2) {
       e.preventDefault();
       const clickedNote = notes.find(n => {
@@ -4923,11 +4923,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
         setNotes(prev => prev.filter(n => n.id !== clickedNote.id));
         setSelectedNoteIds(prev => prev.filter(id => id !== clickedNote.id));
         showToast('Đã xóa nốt!', 'info');
-        return;
       }
-      // Start erase sweep (right-click on empty space only)
-      notesBeforeDragRef.current = JSON.parse(JSON.stringify(notes));
-      setDraggedNote({ mode: 'erase_sweep', visitedPitches: [pitch] });
       return;
     }
 
@@ -5243,6 +5239,9 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
 
   const handleContextMenu = (e) => {
     e.preventDefault();
+    const pos = { x: e.clientX, y: e.clientY, parentKey: null };
+    scaleMenuOriginRef.current = { x: pos.x, y: pos.y };
+    setScaleMenuPos(pos);
   };
 
   const ccDragRef = React.useRef(null);
@@ -5364,12 +5363,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
               } catch (err) { console.error('playNote error:', err); }
             }
           },
-          onMouseUp: () => { keybedMouseDownRef.current = false; },
-          onContextMenu: (e) => {
-            e.preventDefault();
-            e.stopPropagation();
-            setScaleMenuPos({ x: e.clientX, y: e.clientY, parentKey: null });
-          }
+          onMouseUp: () => { keybedMouseDownRef.current = false; }
         }, showLabel && label)
       );
     }
@@ -5449,6 +5443,7 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
   };
   const [selectedScale, setSelectedScale] = React.useState(null);
   const [scaleMenuPos, setScaleMenuPos] = React.useState(null);
+  const scaleMenuOriginRef = React.useRef(null);
   const [aiPrompt, setAiPrompt] = React.useState('');
   const [aiLoading, setAiLoading] = React.useState(false);
   const [showCC, setShowCC] = React.useState(true);
@@ -5533,7 +5528,8 @@ const PianoRollTabEditor = ({ st, zoom, bpm, viewportWidth, onClose, onUpdateNot
         const parentKey = key;
         const isOpen = scaleMenuPos && scaleMenuPos.parentKey === parentKey;
         pushItem(key + " ▸", () => setSelectedScale(null), false, () => {
-          setScaleMenuPos({ x: scaleMenuPos.x + 120, y: scaleMenuPos.y, parentKey });
+          const origin = scaleMenuOriginRef.current || scaleMenuPos;
+          setScaleMenuPos({ x: origin.x + 140, y: origin.y, parentKey });
         });
         if (isOpen) {
           Object.keys(val).forEach(subKey => {