- Create universal activity_yaml_validator.py for validating activity configurations
- Add validation for metadata operations (metadata_add, metadata_remove, metadata_feedback_filter, etc.)
- Validate terminal steps cannot have questions or buckets
- Check Python syntax in processing_script and pre_script blocks
- Validate YAML structure, transitions, and logic flow
- Add 17 comprehensive unit tests with 100% pass rate
- Include test fixtures for validation testing
- Support both CLI and programmatic usage