Motivation
Running usethis from the project venv can cause problems with uv because uv want to be able to delete the venv, but if usethis is running from within that venv it causes permissions errors.

Summary of desired enhancement
I think it should be possible to somehow get usethis to move the current process out of the venv before calling uv.
Otherwise, we can just detect when this is happening and raise a warning/error, and encourage using uvx usethis instead.