chore: remove multi-track demo page

Removed /multi-track-demo route as multi-track functionality is now fully integrated into the main AudioEditor view.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/multi-track-demo/page.tsx

@@ -1,127 +0,0 @@
-'use client';
-
-import * as React from 'react';
-import { TrackList } from '@/components/tracks/TrackList';
-import { useMultiTrack } from '@/lib/hooks/useMultiTrack';
-import { useMultiTrackPlayer } from '@/lib/hooks/useMultiTrackPlayer';
-import { Button } from '@/components/ui/Button';
-import { Play, Pause, Square, SkipBack } from 'lucide-react';
-import { formatDuration } from '@/lib/audio/decoder';
-
-export default function MultiTrackDemoPage() {
-  const {
-    tracks,
-    addTrack,
-    addTrackFromBuffer,
-    removeTrack,
-    updateTrack,
-    clearTracks,
-  } = useMultiTrack();
-
-  const {
-    isPlaying,
-    currentTime,
-    duration,
-    play,
-    pause,
-    stop,
-    seek,
-    togglePlayPause,
-  } = useMultiTrackPlayer(tracks);
-
-  const [zoom, setZoom] = React.useState(1);
-
-  return (
-    <div className="h-screen flex flex-col bg-background">
-      {/* Header */}
-      <div className="h-14 border-b border-border bg-card flex items-center justify-between px-4">
-        <h1 className="text-lg font-semibold">Multi-Track Demo</h1>
-        <div className="flex items-center gap-2">
-          <Button
-            variant="outline"
-            size="sm"
-            onClick={clearTracks}
-            disabled={tracks.length === 0}
-          >
-            Clear All Tracks
-          </Button>
-          <Button
-            variant="outline"
-            size="sm"
-            onClick={() => setZoom((z) => Math.max(0.5, z - 0.5))}
-          >
-            Zoom Out
-          </Button>
-          <Button
-            variant="outline"
-            size="sm"
-            onClick={() => setZoom((z) => Math.min(10, z + 0.5))}
-          >
-            Zoom In
-          </Button>
-        </div>
-      </div>
-
-      {/* Track List */}
-      <div className="flex-1 overflow-hidden">
-        <TrackList
-          tracks={tracks}
-          zoom={zoom}
-          currentTime={currentTime}
-          duration={duration}
-          onAddTrack={() => addTrack()}
-          onImportTrack={(buffer, name) => addTrackFromBuffer(buffer, name)}
-          onRemoveTrack={removeTrack}
-          onUpdateTrack={updateTrack}
-          onSeek={seek}
-        />
-      </div>
-
-      {/* Playback Controls */}
-      <div className="h-16 border-t border-border bg-card flex items-center justify-between px-4">
-        <div className="flex items-center gap-2">
-          <Button
-            variant="outline"
-            size="icon"
-            onClick={stop}
-            disabled={!duration}
-            title="Stop"
-          >
-            <Square className="h-4 w-4" />
-          </Button>
-          <Button
-            variant="outline"
-            size="icon"
-            onClick={togglePlayPause}
-            disabled={!duration}
-            title={isPlaying ? 'Pause' : 'Play'}
-          >
-            {isPlaying ? (
-              <Pause className="h-4 w-4" />
-            ) : (
-              <Play className="h-4 w-4" />
-            )}
-          </Button>
-          <Button
-            variant="outline"
-            size="icon"
-            onClick={() => seek(0)}
-            disabled={!duration}
-            title="Skip to Start"
-          >
-            <SkipBack className="h-4 w-4" />
-          </Button>
-        </div>
-
-        <div className="flex items-center gap-4">
-          <span className="text-sm font-mono">
-            {formatDuration(currentTime)} / {formatDuration(duration)}
-          </span>
-          <span className="text-sm text-muted-foreground">
-            {tracks.length} {tracks.length === 1 ? 'track' : 'tracks'}
-          </span>
-        </div>
-      </div>
-    </div>
-  );
-}