fix: remove pan separator and make effects container full width

- Removed border-t border-border from devices section
- Added negative margin (-mx-3) and padding (px-3) to effects container
  to make it extend full width of the track control panel

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

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

components/tracks/Track.tsx

@@ -390,7 +390,7 @@ export function Track({
             </div>
 
             {/* Devices/Effects Section */}
-            <div className="pt-2 border-t border-border">
+            <div className="pt-2">
               <div className="flex items-center justify-between mb-2">
                 <span className="text-xs font-medium text-muted-foreground uppercase">
                   Devices ({track.effectChain.effects.length})
@@ -407,7 +407,7 @@ export function Track({
               </div>
 
               {/* Horizontal scrolling device rack */}
-              <div className="overflow-x-auto custom-scrollbar">
+              <div className="overflow-x-auto custom-scrollbar -mx-3 px-3">
                 <div className="flex gap-2 pb-2">
                   {track.effectChain.effects.length === 0 ? (
                     <div className="text-xs text-muted-foreground text-center py-4 w-full">