fix: remove gap between automation and effects bars

- Remove border-t from automation bar to eliminate gap with effects bar

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

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

components/tracks/TrackList.tsx

@@ -372,7 +372,7 @@ export function TrackList({
                   {/* Automation Bar - Collapsible, above effects bar at bottom */}
                   {!track.collapsed && (
                     <div
-                      className="absolute left-0 right-0 z-10 pointer-events-auto bg-card/90 backdrop-blur-sm border-t border-border"
+                      className="absolute left-0 right-0 z-10 pointer-events-auto bg-card/90 backdrop-blur-sm"
                       style={{
                         bottom: track.effectsExpanded ? '232px' : '32px' // 32px effects header, or 232px if expanded
                       }}