BargeControls component with 4 states: idle → connecting → connected → ended.
Connected state shows Listen/Whisper/Barge mode tabs (DTMF 4/5/6), live
duration counter, hang up button. Auto-cleanup on unmount. Mode changes
notify sidecar for agent SSE events.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>