docs: Add CI to check that man pages are committed

[thgoebel]

This PR simplifies the pull request template by automating the "man page modified" check. (The "man page added/removed" case I didn't cover, because I don't want to mess with shell magic right now.)

This PR depends on #979 because it uses "make man", and thus relies on "uv run" being in the Makefile. Hence the Makefile is also in the list of changed paths, to catch Makefile edits that might break this Action.

---

• If you are changing Rust code or integration tests (Cargo.*, crates/, etc/, integration-tests/, src/):

  • Did you run the integration tests with act through the act-wrapper (as described in TESTING.md)?

• If you are adding/deleting man pages:

  • Did you update the man_pages config in doc/manual/source/conf.py?
  • Did you update the packaged man pages in the Cargo.toml?
  • Did you commit the freshly built man pages?

• If you are modifying man pages:

  • Did you commit the updated built man pages?

[thgoebel]

You can see an example here: https://github.com/thgoebel/cascade/actions/runs/33070959056/job/98512775383

I also pushed a dummy commit that I will drop before we merge this. Once a maintainer approves the new workflow, we will see if its runs correctly in a pull_request context.

[bal-e]

This looks great! It's nice to trim down the number of simple, repetitive actions involved in contribution.

I have a few comments regarding the CI workflow, let me know what you think.

Also, I guess you'll have to rebase the PR on main now that #979 is merged.

[bal-e]

I would prefer to pull in as little new code as possible, even though you've taken the nice step of locking the commit. Would apt install uv work? Even better: maybe a recent(-ish) version of uv is pre-installed on the CI runner, and this step can be omitted?

[thgoebel]

I didn't see uv being packaged in apt, but there is an unofficial snap by a Canonical employee.
That said, imho using https://github.com/astral-sh/setup-uv is fine, since it is maintained by Astral, the authors of uv.