refactor: remove master effects section, add TODO note

Removed the master effects section from AudioEditor footer:
- Simplified footer to only show transport controls
- Removed master channel strip area
- Removed border separator between sections

Added note to PLAN.md:
- 🔲 Master channel effects (TODO)
- Will implement master effect chain UI later
- Similar to per-track effects but for final mix
- Documented in Phase 7 multi-track features section

This cleans up the UI for now - we'll add master effects
with a proper device rack UI later, similar to how per-track
effects work (collapsible section with horizontal device cards).

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

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

PLAN.md

@@ -94,6 +94,12 @@
 - ✅ Synchronized playback across all tracks
 - ✅ Per-track gain and pan during playback
 - ✅ Solo/Mute handling during playback
+- ✅ Per-track effect chains with device rack
+- ✅ Collapsible effects section below each track
+- ✅ Effect browser with categorized effects
+- ✅ Horizontal scrolling device rack (Ableton-style)
+- ✅ Individual effect cards with expand/collapse
+- 🔲 Master channel effects (TODO: Implement master effect chain UI similar to per-track effects)
 
 ### Next Steps
 - **Phase 6**: Audio effects ✅ COMPLETE (Basic + Filters + Dynamics + Time-Based + Advanced + Chain Management)

components/editor/AudioEditor.tsx

@@ -328,10 +328,8 @@ export function AudioEditor() {
         </main>
       </div>
 
-      {/* Transport Controls + Master Channel */}
-      <div className="border-t border-border bg-card">
       {/* Transport Controls */}
-        <div className="p-3 flex justify-center border-b border-border">
+      <div className="border-t border-border bg-card p-3 flex justify-center">
         <PlaybackControls
           isPlaying={isPlaying}
           isPaused={!isPlaying}
@@ -348,19 +346,6 @@ export function AudioEditor() {
         />
       </div>
 
-        {/* Master Track Strip */}
-        <div className="p-3">
-          <div className="flex items-center gap-2 mb-2">
-            <h3 className="text-sm font-semibold text-foreground">Master</h3>
-            <span className="text-xs text-muted-foreground">Final mix output</span>
-          </div>
-          {/* Master effects will go here */}
-          <div className="text-xs text-muted-foreground">
-            Master effects: {masterEffectChain.effects.length}
-          </div>
-        </div>
-      </div>
-
       {/* Import Track Dialog */}
       <ImportTrackDialog
         open={importDialogOpen}