Move dev tools out of runtime dependencies

[Mirochill]

Summary

• Remove pre-commit, pytest, and the unused packaging dependency from runtime dependencies.
• Keep pre-commit in the dev dependency group, where pytest already lives.
• Update the editable package metadata in uv.lock to match pyproject.toml.

Validation

• git diff --check
• git diff --cached --check
• Reviewed rg --line-number packaging|pre-commit|pytest|pkg_resources|parse_version pyproject.toml sphinx_simplepdf tests docs .github uv.lock
• Not run locally

Closes #138