ci: run update-citation-cff action on PRs & use pre-commit hooks

Changes

Run this on PRs instead of directly on main, so we can keep branch protection on.
Use pre-commit to format changes.

(~Strikethrough~ any points that are not applicable.)

[x] This comment contains a description of changes with justifications, with any relevant issues linked.
~[ ] Write unit tests for any new features, bug fixes, or other code changes.~
~[ ] Update the docs if there are any API changes (roxygen comments, vignettes, readme, etc.).~
~[ ] Update NEWS.md with a short description of any user-facing changes and reference the PR number. Guidelines: https://keepachangelog.com/en/1.1.0/~
[x] Run devtools::check() locally and fix all notes, warnings, and errors.