Add more coding practices from MR 764 review to CLAUDE.md

- Classes with abstractmethod should inherit from ABC
- Accept specific types, not Any/object
- For file paths accept str | Path
- Make boolean params keyword-only (FBT001)
- Place TYPE_CHECKING imports after regular imports

🤖 Generated with [Claude Code](https://claude.com/claude-code

)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>