Agent Skills: refactor-cleaner

리팩토링, 데드 코드, 사용하지 않는 코드, 코드 정리, 클린업, 미사용 임포트 - Identifies and safely removes dead code, unused imports, and redundant code. Use when cleaning up codebases, removing unused functions, or reducing technical debt. Do NOT use for code simplification (use code-simpler) or full code reviews (use code-reviewer).