fix: show Plus button only when effects panel is expanded

- Plus button now conditionally rendered based on track.effectsExpanded
- Matches automation controls behavior
- Cleaner UI when panel is collapsed

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

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

components/tracks/TrackList.tsx

@@ -660,16 +660,18 @@ export function TrackList({
                           ))}
                         </div>
 
-                        {/* Add effect button */}
-                        <Button
-                          variant="ghost"
-                          size="icon-sm"
-                          onClick={() => setEffectBrowserTrackId(track.id)}
-                          title="Add effect"
-                          className="h-5 w-5 flex-shrink-0"
-                        >
-                          <Plus className="h-3 w-3" />
-                        </Button>
+                        {/* Add effect button - only visible when expanded */}
+                        {track.effectsExpanded && (
+                          <Button
+                            variant="ghost"
+                            size="icon-sm"
+                            onClick={() => setEffectBrowserTrackId(track.id)}
+                            title="Add effect"
+                            className="h-5 w-5 flex-shrink-0"
+                          >
+                            <Plus className="h-3 w-3" />
+                          </Button>
+                        )}
 
                         {/* Show/hide toggle */}
                         <Button