Consider reducing the size of our development environment?

[jhkennedy]

Now that we've leaned into nox, we don't necessarily need everything in our development environment as nox will set up isolated testing environments for each session.

So, I think we should consider dropping:

1. the docs optional dependency group from our development environment (venv instructions and conda environment.yml) as the dependencies are rather heavy-weight, and freshly creating the environment can take ~10 minutes (Development Setup Instructions Not Working on Windows #858). running nox -s serve-docs I would expect to be sufficient for most, if not all, of our contributors
2. the tests dependency group could also be dropped from our development environment (venv instructions and conda environment.yml) as the dev group gets you uv and nox, which is all that's needed to run all of our nox sessions. However:
   • the test group is pretty light weight so wouldn't save much
   • this would impact IDE users and contributors who like to call our testing tools directly (e.g., pytest and mypy). In Refactor development guide #874, I've proposed an "IDE setup" section where we could add a line about installing the test dependencies to mitigate this.

Overall I think we should do (1), but as an IDE user, I'd rather not do (2). I felt (2) at least merited discussion, however.