re-enable the minimum versions ci

[keewis]

• follow-up to Migrate development workflow to Pixi #10888 and Bump the actions group with 5 updates #11016

minimum-dependency-versions has recently gained support for pixi envs, which means we can re-enable it.

[keewis]

that's curious, I wouldn't have imagined that the action would fail to install entirely because actions only shallow-clone (breaking the dynamic versioning implemented by setuptools-scm / hatch-vcs). It's probably time to package the module in the action and publish that to PyPI, then deprecate the action entirely (or make the action use the published package).

[keewis]

with the most recent changes (including removing the action in favor of a CLI), the min-versions policy works again. An additional upside is that running pixi run policy will check all policy files locally, which should make the dev experience for min-deps changes nicer.

This is thus ready for review and merging.