Show optimistic active branch during checkout and branch creation

- use `useOptimistic` in `BranchToolbar` to update active branch immediately
- keep optimistic branch in sync on success and roll back on mutation errors
b81ec02984Julius Marminge committed on 3/3/2026, 2:53:21 AM· committed by Julius Marmingeparentde61c0c
1 file changedLine totals unavailable