Add Python 3.14 support

[tobiasdiez]

• Add Python 3.14 to CI
• Fix compilation under 3.14t by using _Py_REFCNT instead of direct ob_refcnt access
• Update uv lock file to use new cysignals

Fixes #191

[dimpase]

oops, I overlooked this one, see #191

I thought that we already have 3.14(non-t) support, so I started adding 3.14(non-t) to the CI...

[dimpase]

As I see, I already pushed 2.2.3 tag :-(

[dimpase]

it does build, but does it actually work?

[dimpase]

tests fail on 3.14, see
https://github.com/sagemath/cypari2/actions/runs/18956854783/job/54135605384

[tobiasdiez]

@dimpase should work now with this PR

[dimpase]

there seems to be a CI bug: tests only run on a tag push, not on a PR merge

[dimpase]

more precisely, build+test is run on a PR being submitted, but it's not run on pushes which don't push a tag.

[tobiasdiez]

yes, I'll open another PR that fixes this.
As preparation for this, could you please rename the master branch to main?

[dimpase]

yes, I'll open another PR that fixes this. As preparation for this, could you please rename the master branch to main?

done, see #192

[dimpase]

@tobiasdiez - can we release now, or you want more PRs merged?

[tobiasdiez]

You can release now in my opinion, fixing the CI doesn't require a new release anyway and I don't think anything else is planned.