fix: lỗi alt-click drag nhân bản

app/templates/index.html

@@ -363,7 +363,7 @@
                             canvasRef.current.style.cursor = isOverClip ? 'cell' : 'not-allowed';
                         } else {
                             // select tool
-                            canvasRef.current.style.cursor = (isOverClip && e.altKey) ? 'grab' : 'crosshair';
+                            canvasRef.current.style.cursor = (isOverClip && (e.altKey || e.ctrlKey)) ? 'grab' : 'crosshair';
                         }
                     }}
                     onMouseDown={(e) => {
@@ -401,7 +401,7 @@
                                 e.preventDefault();
                                 e.stopPropagation();
                                 if (onClipDragStart) {
-                                    onClipDragStart(track.id, clickedClip.id, time - clickedClip.startTime);
+                                    onClipDragStart(track.id, clickedClip.id, time - clickedClip.startTime, e.ctrlKey);
                                 }
                             } else {
                                 onPlayheadSet(time);
@@ -409,12 +409,12 @@
                             return;
                         }
 
-                        // Check for click drag clip (no Ctrl key required if select tool is in fallback ctrl-mode)
+                        // Check for click drag clip (Alt to move, Ctrl to duplicate)
-                        if (clickedClip && e.ctrlKey) {
+                        if (clickedClip && (e.altKey || e.ctrlKey)) {
                             e.preventDefault();
                             e.stopPropagation();
                             if (onClipDragStart) {
-                                onClipDragStart(track.id, clickedClip.id, time - clickedClip.startTime);
+                                onClipDragStart(track.id, clickedClip.id, time - clickedClip.startTime, e.ctrlKey);
                             }
                             return;
                         }
@@ -1710,25 +1710,64 @@
             const captureTrackSnapshotRef = useRef(null);
             captureTrackSnapshotRef.current = captureTrackSnapshot;
 
-            const handleClipDragStart = (trackId, clipId, clickOffset) => {
+            const handleClipDragStart = (trackId, clipId, clickOffset, isDuplicate = false) => {
                 const track = tracks.find(t => t.id === trackId);
                 if (!track) return;
                 
-                const clips = track.clips && track.clips.length > 0 ? track.clips : (track.buffer ? [{
+                const existingClips = track.clips && track.clips.length > 0 ? track.clips : (track.buffer ? [{
-                    id: 'default',
+                    id: 'default_' + track.id,
                     buffer: track.buffer,
                     startTime: track.startTime || 0,
                     name: track.name
                 }] : []);
                 
-                const clip = clips.find(c => c.id === clipId);
+                const clip = existingClips.find(c => c.id === clipId || (clipId === 'default' && c.id === 'default_' + track.id));
                 if (!clip) return;
                 
                 const beforeSnap = captureTrackSnapshot(trackId);
                 
+                let targetClipId = clip.id;
+                
+                if (isDuplicate) {
+                    const cloneId = clip.id + '_copy_' + Date.now();
+                    const clone = {
+                        ...clip,
+                        id: cloneId,
+                        name: clip.name + ' (Copy)'
+                    };
+                    
+                    setTracks(prev => prev.map(t => {
+                        if (t.id === trackId) {
+                            const newClips = [...existingClips, clone];
+                            return {
+                                ...t,
+                                clips: newClips,
+                                buffer: newClips[0].buffer,
+                                startTime: newClips[0].startTime,
+                                name: newClips[0].name
+                            };
+                        }
+                        return t;
+                    }));
+                    
+                    targetClipId = cloneId;
+                } else {
+                    if (!track.clips || track.clips.length === 0) {
+                        setTracks(prev => prev.map(t => {
+                            if (t.id === trackId) {
+                                return {
+                                    ...t,
+                                    clips: existingClips
+                                };
+                            }
+                            return t;
+                        }));
+                    }
+                }
+                
                 setDraggedClip({
                     trackId: trackId,
-                    clipId: clipId,
+                    clipId: targetClipId,
                     clickOffset: clickOffset,
                     buffer: clip.buffer,
                     name: clip.name,
@@ -2789,7 +2828,7 @@
                                         <button 
                                             onClick={() => { setActiveTool('select'); showToast('Công cụ chọn (Select Tool) đã kích hoạt.', 'info'); }}
                                             className={`p-1 rounded transition text-xs flex items-center justify-center ${activeTool === 'select' ? 'bg-cyan-950/80 text-cyan-400 border border-cyan-800/50 font-bold' : 'text-zinc-400 hover:bg-zinc-800 border border-transparent'}`}
-                                            title="Select Tool: Chọn khoảng, Đặt playhead (Giữ Ctrl kéo để di chuyển nhanh clip)"
+                                            title="Select Tool: Chọn khoảng, Đặt playhead (Alt+Kéo để di chuyển clip, Ctrl+Kéo để nhân bản)"
                                         >
                                             <i data-lucide="mouse-pointer" className="w-3 h-3"></i>
                                         </button>