feat: 플레이어 다운/넉백 피격 반응 추가

Assets/_Game/Scripts/Skills/Effects/DownEffect.cs

@@ -0,0 +1,42 @@
+using UnityEngine;
+
+using Colosseum.Player;
+
+namespace Colosseum.Skills.Effects
+{
+    /// <summary>
+    /// 대상에게 다운 상태를 적용하는 스킬 효과입니다.
+    /// </summary>
+    [CreateAssetMenu(fileName = "DownEffect", menuName = "Colosseum/Skills/Effects/Down")]
+    public class DownEffect : SkillEffect
+    {
+        [Header("Settings")]
+        [Tooltip("다운 지속 시간")]
+        [Min(0f)] [SerializeField] private float duration = 1f;
+
+        /// <summary>
+        /// 다운 지속 시간
+        /// </summary>
+        public float Duration => duration;
+
+        /// <summary>
+        /// 다운 효과를 적용합니다.
+        /// </summary>
+        protected override void ApplyEffect(GameObject source, GameObject target)
+        {
+            if (target == null)
+            {
+                Debug.LogWarning("[DownEffect] Target is null.");
+                return;
+            }
+
+            if (!target.TryGetComponent(out HitReactionController hitReactionController))
+            {
+                Debug.LogWarning($"[DownEffect] HitReactionController not found on target: {target.name}");
+                return;
+            }
+
+            hitReactionController.ApplyDown(duration);
+        }
+    }
+}