refactor(scripts): abstract clean-world scripts with shared utilities and modular structure

- Create clean-world/ directory with modular scripts
- Add clean-world-utils.mjs with shared functions (deleteFileLocal, deleteFileS3, etc.)
- Refactor clean-world-local.mjs and clean-world-s3.mjs to use shared utilities
- Update main clean-world.mjs to dynamically import appropriate script
- Add README.md with documentation for the new structure
- Fix path resolution issues for world directories
- Maintain backward compatibility with npm run world:clean

This addresses the reviewer's suggestion to avoid code duplication and ensure both storage types stay in sync when cleanup logic changes.

Author: DevStarlight