Enforce Python quality checks

[kevinten10]

What changed

• Formatted the current package and removed unused imports.
• Added Black, isort, and flake8 CI enforcement.
• Pinned mypy to the range that still checks the Python 3.8 API target.
• Updated development instructions and removed a personal package-author email.

Why

README-listed quality commands failed on the default branch, and current mypy releases no longer accept the declared Python 3.8 target.

Validation

• Black, isort, flake8, and mypy pass
• 24 pytest tests pass
• Wheel build and public import smoke test pass
• README links pass