Modernize pre-commit quality checks

[Pulserius]

Summary

Modernizes FedGraph's pre-commit toolchain and documents its workflow.

• Updates pinned pre-commit hooks for the current development environment.
• Adds Black-compatible isort and Python 3.9-targeted Mypy settings.
• Adds the development dependency group required for local quality checks.
• Applies required formatting and narrowly scoped typing guidance.
• Documents triggers, configured hooks, related configuration files, and the boundary between pre-commit and pytest.

Why

The previous hook versions and type-checking setup no longer passed reliably with the current FedGraph development environment.

Validation

• python -m pre_commit run --all-files
• git diff --check