tests: pre-commit does not run linting and mypy on tests and examples

[ajbozarth]

pre-commit and CI only running ruff check and mypy on the mellea/ dir, unlike ruff format which runs on the entire project. We should be consistent with our code checks across the repo.

[ajbozarth]

This was found while writing the docs in #369

[ajbozarth]

FYI I am working on this, will assign to myself once I get triage perms