* Fix the PATH mangling in action.yml
Let's put the `uv` on PATH question aside, and fix#2663.
This change ensures that the PATH entries added by Github when you request `shell: bash` don't make it into the pwsh environment. It also keeps the uv binary on PATH if installed via `extras:`.
Would love to get this fixed soon, then we can figure out the right approach regarding `uv` discovery.
* Modify script to allow testing of the GHA action on a PR
Cherry-picked from #2718 and modified so we can test the action.yml file