test-invoke-pip
- Updates triggers for UI workflow `lint-frontend` - Corrects UI paths for `test-invoke-pip` and `test-invoke-pip-skip`
- filter paths for `build-container.yml` and `test-invoke-pip.yml` - add workflow to pass required checks on PRs with `paths-ignore` - this triggers if `test-invoke-pip.yml` does not - fix "CI checks on main link" in `/README.md`