use uv to manage Python installation and run scripts

[zacharyburnett]

• internally, when loading tox environments, we can use setup-uv instead of setup-python (and uvx instead of pipx) to run scripts
• when provisioning the base Python installation from which to call tox -e, we can also use setup-uv instead of setup-python. This does NOT force the user to use tox-uv in their tox.ini, though they can if they want to
• when building a Micromamba environment, we can set the use_uv: true config entry in .condarc to tell Mamba to use uv instead of pip when resolving the PyPI environment. This is transparent to the user

[Cadair]

Before you spend too much time on this, I'd like to discuss if it's worth it. What's your motivation?

[zacharyburnett]

Before you spend too much time on this, I'd like to discuss if it's worth it. What's your motivation?

since the load tox environments job runs every time before every workflow, it makes sense to optimize it as much as possible (even though it's already pretty fast). To that end, resolving with uv is more performant than pip. Also, micromamba allows using uv to manage PyPI packages installed in the environment (use_uv: true in condarc)

[zacharyburnett]

I figure that, since this script is probably run every few minutes all day every day, even a small performance increase is worth it (but we should at least freeze the version of uv)

[Cadair]

I figure that, since this script is probably run every few minutes all day every day, even a small performance increase is worth it (but we should at least freeze the version of uv)

I can get behind this for the internal stuff, but I don't think we should go into anything tox related?