Add support for free-threaded CPython

[fanninpm]

For more details, see here.

[RuneBlaze]

Got it -- let me work on this tonight (hopefully)

[RuneBlaze]

oki I just vibe-coded all-of-that... tested on:

Python 3.13.7 experimental free-threading build (main, Sep 27 2025, 19:33:14) [Clang 17.0.0 (clang-1700.0.13.5)] on darwin

seemingly it works on that build. Version 0.0.15 is now ready for consumption

[RuneBlaze]

closing this for now... given that already tested on Py 3.13.7 🤔

[RuneBlaze]

@fanninpm actually sorry for the extra-ping -- I have not professionally worked with free-threaded Python before, so if you could test this new version out that would actually be much appreciated.. i tested it locally using a ft build, but that's just me, a single person