Add Python 3.14 free-threaded (cp314t) wheel support

[clemlesne]

Summary

With the release of Python 3.14, the new free-threaded (no-GIL) mode is becoming more widely used. It would be great if PyMuPDF could provide prebuilt wheels and confirm compatibility with python3.14t (the free-threaded ABI).

Current State

• PyMuPDF supports Python 3.14 (standard build) per the changelog
• However, PyPI shows no cp314t wheels for the free-threaded build
• Free-threaded Python uses the cp314t wheel tag (note the t suffix)

What's Needed

1. Update CI (cibuildwheel) to build cp314t wheels
2. Declare GIL compatibility using Py_mod_gil slot in module definition (per PEP 703)
3. Test under free-threaded Python to ensure thread safety

Resources

• Python Free-Threading Guide
• Free-Threaded Wheels Tracker
• PEP 703 – Making the GIL Optional
• cibuildwheel free-threaded docs

[JorjMcKie]

Sorry, we cannot do this due to our internal architecture.
The existence of the GIL never was a reason why we did not support threading. Consequently, the "no-GIL" option means no change either.

[clemlesne]

| The existence of the GIL never was a reason why we did not support threading.

The primary issue there, from my own point of view.

I'm running all the services under 3.14t and there is no pre-built wheel for PyMuPDF. It generates slow builds and frustration using the lib. Publishing a pre-built wheel would make life easier for all lib users.

Cython gives locks (https://cython.readthedocs.io/en/latest/src/userguide/freethreading.html#locks) if some underlying code is not thread safe it could allow to make it no-gil compatible without breaking too much.