git: Touch up amend UX (#35114)

Follow-up to #26114

- Ensure that the previous commit message is filled in when toggling on
amend mode from the context menu
- Fix keybinding flicker in context menu

Release Notes:

- N/A
3dc36dc7c3Cole Miller committed on 7/28/2025, 4:21:07 PM· committed by GitHubparentfd68265
4 files changedLine totals unavailable