Add git checkout support and clear errors on success

Wire up git:checkout IPC channel across the full stack so branch
selection actually checks out the branch. Clear error banners when
a subsequent checkout or branch creation succeeds.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
59448593d8Julius Marminge committed on 2/11/2026, 5:00:18 PMparent3047974
2 files changedLine totals unavailable