git_graph: Remove horizontal scrolling from canvas (#53082)

I also added a keybinding to focus the search bar.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

Closes #ISSUE

Release Notes:

- N/A or Added/Fixed/Improved ...
e93beb05c4Anthony Eid committed on 4/3/2026, 5:33:50 PM· committed by GitHubparentbde6a01
1 file changedLine totals unavailable