Add support for Python 3.14

[hugovk]

We still need to support 3.12 because that's what on the downloads server, but there are now enough 3.14 wheels to start testing it.

[AA-Turner]

Could we consider using pylock.toml here over the pip-compile txt files with many hashes?

A

[hugovk]

I'd be fine using uv, but pip only supports writing pylock.toml and not yet reading.

pip support pypa/pip#13334 depends on pypa/pip#13369 for the first step, which depends on pypa/packaging#950 which depends on pypa/packaging.python.org#1971.

@pablogsal @Yhg1s Are you okay using uv here, or do you prefer to stick with pip?

[Yhg1s]

Since we already have it in place, I think it'd be easier to stick with pip. (I don't currently have uv installed on my build system.) If there's a compelling reason to switch I'm fine with it, though.

[hugovk]

Okay, let's stick with the current pip system and we can switch to pylock.toml when pip supports it or there's a better reason to use uv.

[webknjaz]

FTR, I want to support pylock in pip-tools as well, eventually: jazzband/pip-tools#2124.