Reuse existing logic used to generate commit messages to disable commit buttons (#26034)

Also
- Recomputes `suggested_commit_message` and no longer stores it, to
ensure things are always up to date
- Reduces indentation in `render_footer`

Release Notes:

- N/A
76a81607deJoseph T. Lyons committed on 3/4/2025, 1:50:53 PM· committed by GitHubparent7d22059
2 files changedLine totals unavailable