Add comprehensive section on SQLAlchemy fixture best practices:
- Explain why db.expunge() is an anti-pattern in test fixtures
- Document how test isolation works via the db fixture
- Provide examples of correct vs incorrect fixture patterns
- Show how to use db.refresh() for fresh data instead of expunge
This documents the lessons learned from the fixture refactoring
and helps prevent future issues with DetachedInstanceError.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
