feat: redesign track layout to DAW-style with left control panel

Major UX improvement inspired by Audacity/Ableton Live:

- Each track now has 2 sections: left control panel (fixed 288px) and right waveform (flexible)
- Left panel contains: track name, color indicator, collapse toggle, volume, pan, solo, mute, delete
- TrackHeader component functionality moved directly into Track component
- Removed redundant track controls from SidePanel
- SidePanel now simplified to show global actions and effect chain
- Track controls are always visible on the left, waveform scrolls horizontally on the right
- Collapsed tracks show only the header row (48px height)
- Much better UX for multi-track editing

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

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

components/layout/SidePanel.tsx

@@ -9,13 +9,10 @@ import {
   Trash2,
   Link2,
   FolderOpen,
-  Volume2,
   Music2,
 } from 'lucide-react';
 import { Button } from '@/components/ui/Button';
-import { Slider } from '@/components/ui/Slider';
 import { cn } from '@/lib/utils/cn';
-import { formatDuration } from '@/lib/audio/decoder';
 import type { Track } from '@/types/track';
 import type { EffectChain, EffectPreset } from '@/lib/audio/effects/chain';
 import { EffectRack } from '@/components/effects/EffectRack';
@@ -165,122 +162,17 @@ export function SidePanel({
               )}
             </div>
 
-            {/* Track List */}
+            {/* Track List - Simplified */}
             {tracks.length > 0 ? (
               <div className="space-y-2">
                 <h3 className="text-xs font-semibold text-muted-foreground uppercase">
                   Tracks ({tracks.length})
                 </h3>
-                <div className="space-y-2">
-                  {tracks.map((track) => {
-                    const isSelected = selectedTrackId === track.id;
-                    return (
-                      <div
-                        key={track.id}
-                        className={cn(
-                          'p-3 rounded-lg border transition-colors cursor-pointer',
-                          isSelected
-                            ? 'bg-primary/10 border-primary'
-                            : 'bg-secondary/30 border-border hover:border-primary/50'
-                        )}
-                        onClick={() => onSelectTrack(isSelected ? null : track.id)}
-                      >
-                        <div className="flex items-center justify-between mb-2">
-                          <div className="flex-1 min-w-0">
-                            <div className="text-sm font-medium text-foreground truncate">
-                              {String(track.name || 'Untitled Track')}
-                            </div>
-                            {track.audioBuffer && (
-                              <div className="text-xs text-muted-foreground">
-                                {formatDuration(track.audioBuffer.duration)}
-                              </div>
-                            )}
-                          </div>
-                          <Button
-                            variant="ghost"
-                            size="icon-sm"
-                            onClick={(e) => {
-                              e.stopPropagation();
-                              onRemoveTrack(track.id);
-                            }}
-                            title="Remove track"
-                          >
-                            <Trash2 className="h-3.5 w-3.5 text-destructive" />
-                          </Button>
-                        </div>
-
-                        {/* Track Controls - Always visible */}
-                        <div className="space-y-2" onClick={(e) => e.stopPropagation()}>
-                          {/* Volume */}
-                          <div className="space-y-1">
-                            <div className="flex items-center justify-between">
-                              <label className="text-xs text-muted-foreground flex items-center gap-1">
-                                <Volume2 className="h-3 w-3" />
-                                Volume
-                              </label>
-                              <span className="text-xs text-muted-foreground">
-                                {Math.round(track.volume * 100)}%
-                              </span>
-                            </div>
-                            <Slider
-                              value={track.volume}
-                              onChange={(value) => onUpdateTrack(track.id, { volume: value })}
-                              min={0}
-                              max={1}
-                              step={0.01}
-                            />
-                          </div>
-
-                          {/* Pan */}
-                          <div className="space-y-1">
-                            <div className="flex items-center justify-between">
-                              <label className="text-xs text-muted-foreground">Pan</label>
-                              <span className="text-xs text-muted-foreground">
-                                {track.pan === 0
-                                  ? 'C'
-                                  : track.pan < 0
-                                  ? `L${Math.round(Math.abs(track.pan) * 100)}`
-                                  : `R${Math.round(track.pan * 100)}`}
-                              </span>
-                            </div>
-                            <Slider
-                              value={track.pan}
-                              onChange={(value) => onUpdateTrack(track.id, { pan: value })}
-                              min={-1}
-                              max={1}
-                              step={0.01}
-                            />
-                          </div>
-
-                          {/* Solo / Mute */}
-                          <div className="flex gap-2">
-                            <Button
-                              variant={track.solo ? 'default' : 'outline'}
-                              size="sm"
-                              onClick={(e) => {
-                                e.stopPropagation();
-                                onUpdateTrack(track.id, { solo: !track.solo });
-                              }}
-                              className="flex-1 text-xs"
-                            >
-                              Solo
-                            </Button>
-                            <Button
-                              variant={track.mute ? 'default' : 'outline'}
-                              size="sm"
-                              onClick={(e) => {
-                                e.stopPropagation();
-                                onUpdateTrack(track.id, { mute: !track.mute });
-                              }}
-                              className="flex-1 text-xs"
-                            >
-                              Mute
-                            </Button>
-                          </div>
-                        </div>
-                      </div>
-                    );
-                  })}
+                <div className="text-xs text-muted-foreground">
+                  <p className="mb-2">
+                    Track controls are located on the left side of each track in the timeline.
+                  </p>
+                  <p>Click a track to select it and apply effects from the Effect Chain tab.</p>
                 </div>
               </div>
             ) : (

components/tracks/Track.tsx

@@ -1,8 +1,10 @@
 'use client';
 
 import * as React from 'react';
+import { Volume2, VolumeX, Headphones, Trash2, ChevronDown, ChevronRight } from 'lucide-react';
 import type { Track as TrackType } from '@/types/track';
-import { TrackHeader } from './TrackHeader';
+import { Button } from '@/components/ui/Button';
+import { Slider } from '@/components/ui/Slider';
 import { cn } from '@/lib/utils/cn';
 
 export interface TrackProps {
@@ -40,6 +42,39 @@ export function Track({
 }: TrackProps) {
   const canvasRef = React.useRef<HTMLCanvasElement>(null);
   const containerRef = React.useRef<HTMLDivElement>(null);
+  const [isEditingName, setIsEditingName] = React.useState(false);
+  const [nameInput, setNameInput] = React.useState(String(track.name || 'Untitled Track'));
+  const inputRef = React.useRef<HTMLInputElement>(null);
+
+  const handleNameClick = () => {
+    setIsEditingName(true);
+    setNameInput(String(track.name || 'Untitled Track'));
+  };
+
+  const handleNameBlur = () => {
+    setIsEditingName(false);
+    if (nameInput.trim()) {
+      onNameChange(nameInput.trim());
+    } else {
+      setNameInput(String(track.name || 'Untitled Track'));
+    }
+  };
+
+  const handleNameKeyDown = (e: React.KeyboardEvent) => {
+    if (e.key === 'Enter') {
+      inputRef.current?.blur();
+    } else if (e.key === 'Escape') {
+      setNameInput(String(track.name || 'Untitled Track'));
+      setIsEditingName(false);
+    }
+  };
+
+  React.useEffect(() => {
+    if (isEditingName && inputRef.current) {
+      inputRef.current.focus();
+      inputRef.current.select();
+    }
+  }, [isEditingName]);
 
   // Draw waveform
   React.useEffect(() => {
@@ -123,59 +158,173 @@ export function Track({
     onSeek(clickTime);
   };
 
-  if (track.collapsed) {
-    return (
-      <div
-        className={cn(
-          'border-b border-border cursor-pointer',
-          isSelected && 'ring-2 ring-primary ring-inset'
-        )}
-        onClick={onSelect}
-      >
-        <TrackHeader
-          track={track}
-          onToggleMute={onToggleMute}
-          onToggleSolo={onToggleSolo}
-          onToggleCollapse={onToggleCollapse}
-          onVolumeChange={onVolumeChange}
-          onPanChange={onPanChange}
-          onRemove={onRemove}
-          onNameChange={onNameChange}
-        />
-      </div>
-    );
-  }
+  const trackHeight = track.collapsed ? 48 : track.height;
 
   return (
     <div
       ref={containerRef}
       className={cn(
-        'border-b border-border cursor-pointer',
+        'flex border-b border-border',
         isSelected && 'ring-2 ring-primary ring-inset'
       )}
-      onClick={onSelect}
+      style={{ height: trackHeight }}
     >
-      <TrackHeader
-        track={track}
-        onToggleMute={onToggleMute}
-        onToggleSolo={onToggleSolo}
-        onToggleCollapse={onToggleCollapse}
-        onVolumeChange={onVolumeChange}
-        onPanChange={onPanChange}
-        onRemove={onRemove}
-        onNameChange={onNameChange}
-      />
-      <div className="relative" style={{ height: track.height }}>
-        {track.audioBuffer ? (
-          <canvas
-            ref={canvasRef}
-            className="w-full h-full cursor-pointer"
-            onClick={handleCanvasClick}
+      {/* Left: Track Control Panel (Fixed Width) */}
+      <div
+        className="w-72 flex-shrink-0 bg-card border-r border-border p-3 space-y-2 overflow-y-auto"
+        onClick={(e) => e.stopPropagation()}
+      >
+        {/* Track Name & Collapse Toggle */}
+        <div className="flex items-center gap-2">
+          <Button
+            variant="ghost"
+            size="icon-sm"
+            onClick={onToggleCollapse}
+            title={track.collapsed ? 'Expand track' : 'Collapse track'}
+          >
+            {track.collapsed ? (
+              <ChevronRight className="h-4 w-4" />
+            ) : (
+              <ChevronDown className="h-4 w-4" />
+            )}
+          </Button>
+
+          <div
+            className="w-1 h-8 rounded-full flex-shrink-0"
+            style={{ backgroundColor: track.color }}
           />
-        ) : (
-          <div className="flex items-center justify-center h-full text-sm text-muted-foreground">
-            No audio loaded
+
+          <div className="flex-1 min-w-0">
+            {isEditingName ? (
+              <input
+                ref={inputRef}
+                type="text"
+                value={nameInput}
+                onChange={(e) => setNameInput(e.target.value)}
+                onBlur={handleNameBlur}
+                onKeyDown={handleNameKeyDown}
+                className="w-full px-2 py-1 text-sm font-medium bg-background border border-border rounded"
+              />
+            ) : (
+              <div
+                onClick={handleNameClick}
+                className="px-2 py-1 text-sm font-medium text-foreground truncate cursor-pointer hover:bg-accent rounded"
+                title={String(track.name || 'Untitled Track')}
+              >
+                {String(track.name || 'Untitled Track')}
+              </div>
+            )}
           </div>
+
+          <Button
+            variant="ghost"
+            size="icon-sm"
+            onClick={onRemove}
+            title="Remove track"
+            className="text-destructive hover:text-destructive hover:bg-destructive/10"
+          >
+            <Trash2 className="h-4 w-4" />
+          </Button>
+        </div>
+
+        {/* Track Controls - Only show when not collapsed */}
+        {!track.collapsed && (
+          <>
+            {/* Volume */}
+            <div className="space-y-1">
+              <div className="flex items-center justify-between">
+                <label className="text-xs text-muted-foreground flex items-center gap-1">
+                  <Volume2 className="h-3 w-3" />
+                  Volume
+                </label>
+                <span className="text-xs text-muted-foreground">
+                  {Math.round(track.volume * 100)}%
+                </span>
+              </div>
+              <Slider
+                value={track.volume}
+                onChange={onVolumeChange}
+                min={0}
+                max={1}
+                step={0.01}
+              />
+            </div>
+
+            {/* Pan */}
+            <div className="space-y-1">
+              <div className="flex items-center justify-between">
+                <label className="text-xs text-muted-foreground">Pan</label>
+                <span className="text-xs text-muted-foreground">
+                  {track.pan === 0
+                    ? 'C'
+                    : track.pan < 0
+                    ? `L${Math.round(Math.abs(track.pan) * 100)}`
+                    : `R${Math.round(track.pan * 100)}`}
+                </span>
+              </div>
+              <Slider
+                value={track.pan}
+                onChange={onPanChange}
+                min={-1}
+                max={1}
+                step={0.01}
+              />
+            </div>
+
+            {/* Solo / Mute Buttons */}
+            <div className="flex gap-2">
+              <Button
+                variant={track.solo ? 'default' : 'outline'}
+                size="sm"
+                onClick={onToggleSolo}
+                className={cn(
+                  'flex-1 text-xs',
+                  track.solo && 'bg-yellow-500/20 hover:bg-yellow-500/30 text-yellow-500'
+                )}
+              >
+                <Headphones className="h-3.5 w-3.5 mr-1.5" />
+                Solo
+              </Button>
+              <Button
+                variant={track.mute ? 'default' : 'outline'}
+                size="sm"
+                onClick={onToggleMute}
+                className={cn(
+                  'flex-1 text-xs',
+                  track.mute && 'bg-red-500/20 hover:bg-red-500/30 text-red-500'
+                )}
+              >
+                {track.mute ? (
+                  <VolumeX className="h-3.5 w-3.5 mr-1.5" />
+                ) : (
+                  <Volume2 className="h-3.5 w-3.5 mr-1.5" />
+                )}
+                Mute
+              </Button>
+            </div>
+          </>
+        )}
+      </div>
+
+      {/* Right: Waveform Area (Flexible Width) */}
+      <div
+        className="flex-1 relative bg-slate-900 cursor-pointer"
+        onClick={onSelect}
+      >
+        {!track.collapsed && (
+          <>
+            {track.audioBuffer ? (
+              <canvas
+                ref={canvasRef}
+                className="w-full h-full cursor-pointer"
+                onClick={handleCanvasClick}
+              />
+            ) : (
+              <div className="flex items-center justify-center h-full text-sm text-muted-foreground">
+                No audio loaded
+              </div>
+            )}
+          </>
         )}
       </div>
     </div>