Adopt toggle controls for diff panel and header button

- add reusable `ui/toggle` and `ui/toggle-group` components built on Base UI
- switch diff view mode controls and chat header diff toggle to use the new toggle primitives
867c122082Julius Marminge committed on 2/19/2026, 5:59:17 AM· committed by Julius Marmingeparentcf8a2f0
4 files changedLine totals unavailable