GitHub Actions: Run pytest on Python 3.14

[cclauss]

https://www.python.org/downloads/release/python-3140/
Unfortunately, free threaded Python 3.14t fails, so we will drop back to 3.14 for now.

[Copilot]

Pull Request Overview

This PR updates the GitHub Actions pytest workflow to test against Python 3.14t (the free-threaded build) instead of Python 3.13, enabling validation of the application's compatibility with Python's experimental free-threaded runtime.

Key Changes:

• Replaced Python 3.13 with Python 3.14t in the test matrix

[cclauss]

@overcat, please see the fastcrc==0.3.3 error line 2623 of the Python 3.14t pytest run.

• https://github.com/ArduPilot/MethodicConfigurator/actions/runs/18815585183/job/53683402962?pr=978#step:8:2623

Do we need to add a pytest plugin?

[overcat]

overcat/fastcrc#17
Thank you for reporting this issue. I will release a new version after testing it and confirming there are no problems.

[amilcarlucas]

Cool stuff, thanks @cclauss

[cclauss]

Let's wait for a https://github.com/overcat/fastcrc/releases > v0.3.3.

• https://pypi.org/project/fastcrc

[overcat]

https://pypi.org/project/fastcrc/0.3.4/ is ready.

[amilcarlucas]

I like all the changes, but the tests are failing :(

[cclauss]

Yes. Bottom line seems to be that Matplotlib use of deepcopy() is a blocker.

[amilcarlucas]

I'm trying a workaround here: #980

[amilcarlucas]

OK, 3.14 is fixed on master now, Thanks for working on this.

Please rebase it and try to fix 3.14t if possible

[amilcarlucas]

Thanks, merged.