PR Summary

As noted in #25681, the type hint for intersection was missing the case of None (i.e. no overlap)
Also update the docstring of get_tightbbox which returns the direct output of intersection when clipping.
get_tightbbox was actually already type hinted as Bbox | None, despite the docstring not indicating None as a possibility.

PR Checklist

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• New plotting related features are documented with examples.

Release Notes

• New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst