feat: 플레이어 다운 및 넉백 피격 반응 추가

- HitReactionController로 다운과 넉백 전용 로직을 분리
- 다운 시작, 루프, 회복 애니메이션과 DownEffect를 연결
- 행동 상태와 스킬 취소가 피격 반응과 연동되도록 정리
- 자동 검증 러너에 다운 및 넉백 검증을 추가

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