Add free threaded Python 3.14t to the testing

[cclauss]

No description provided.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.53%. Comparing base (dba6b86) to head (bea5228).
⚠️ Report is 87 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1274   +/-   ##
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  Coverage   90.53%   90.53%           
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  Files           2        2           
  Lines         412      412           
  Branches       45       45           
=======================================
  Hits          373      373           
  Misses         30       30           
  Partials        9        9           

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[seifertm]

Thanks! Let's add 3.14t to the tested versions.

To be honest, I was undecided whether we should explicitly test against the free-threaded version, because I didn't see how it would affect pytest-asyncio.

Do you expect the free-threading build to behave differently with regards to (pytest-)asyncio?

[cclauss]

I am unsure. When I see benchmarks at the bottom of https://py-free-threading.github.io/examples/asyncio I expect that there will be a lot of exploration of using asyncio and free threading together. If this is not needed then we can close.

[seifertm]

Let's merge it, it's a good idea. I was just interested in your perspective.