test: add comprehensive ListFilesTool test suite (40 tests)

Add full test coverage for ListFilesTool including:
- Parameter validation (missing path)
- Basic and recursive file listing
- Approval flow and user cancellation
- Relative and absolute path resolution
- Error handling (nonexistent dirs, permission denied)
- Partial message streaming (handlePartial)
- Edge cases (empty dirs, large file sets, root/dot paths)
- Singleton instance verification
- RooIgnore/RooProtected controller passthrough

Fixes cross-platform compatibility for Windows CI by using
path.resolve() instead of hardcoded Unix paths, and removing
the unnecessary path module mock that caused failures on Windows.

Closes #209

Author: proyectoauraorg