chore: Assets 디렉토리 구조 정리 및 네이밍 컨벤션 적용

- Assets/_Game/ 하위로 게임 에셋 통합
- External/ 패키지 벤더별 분류 (Synty, Animations, UI)
- 에셋 네이밍 컨벤션 확립 및 적용
  (Data_Skill_, Data_SkillEffect_, Prefab_, Anim_, Model_, BT_ 등)
- pre-commit hook으로 네이밍 컨벤션 자동 검사 추가
- RESTRUCTURE_CHECKLIST.md 작성

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -0,0 +1,68 @@
+using UnityEngine;
+
+namespace Colosseum.Skills.Effects
+{
+    /// <summary>
+    /// 프리팹 스폰 효과 (투사체, 파티클 등)
+    /// </summary>
+    [CreateAssetMenu(fileName = "SpawnEffect", menuName = "Colosseum/Skills/Effects/Spawn")]
+    public class SpawnEffect : SkillEffect
+    {
+        [Header("Spawn Settings")]
+        [SerializeField] private GameObject prefab;
+        [SerializeField] private SpawnLocation spawnLocation = SpawnLocation.Caster;
+        [SerializeField] private Vector3 spawnOffset = Vector3.zero;
+        [SerializeField] private bool parentToCaster = false;
+        [Min(0f)] [SerializeField] private float autoDestroyTime = 3f;
+
+        protected override void ApplyEffect(GameObject caster, GameObject target)
+        {
+            if (prefab == null || caster == null) return;
+
+            Vector3 spawnPos = GetSpawnPosition(caster, target) + spawnOffset;
+            Quaternion spawnRot = GetSpawnRotation(caster, target);
+            Transform parent = parentToCaster ? caster.transform : null;
+
+            GameObject instance = Object.Instantiate(prefab, spawnPos, spawnRot, parent);
+
+            // SkillProjectile 컴포넌트가 있으면 초기화
+            var projectile = instance.GetComponent<SkillProjectile>();
+            if (projectile != null)
+            {
+                projectile.Initialize(caster, this);
+            }
+
+            if (autoDestroyTime > 0f)
+            {
+                Object.Destroy(instance, autoDestroyTime);
+            }
+        }
+
+        private Vector3 GetSpawnPosition(GameObject caster, GameObject target)
+        {
+            return spawnLocation switch
+            {
+                SpawnLocation.Caster => caster.transform.position,
+                SpawnLocation.CasterForward => caster.transform.position + caster.transform.forward * 2f,
+                SpawnLocation.Target => target != null ? target.transform.position : caster.transform.position,
+                _ => caster.transform.position
+            };
+        }
+
+        private Quaternion GetSpawnRotation(GameObject caster, GameObject target)
+        {
+            if (spawnLocation == SpawnLocation.Target && target != null)
+            {
+                return Quaternion.LookRotation(target.transform.position - caster.transform.position);
+            }
+            return caster.transform.rotation;
+        }
+    }
+
+    public enum SpawnLocation
+    {
+        Caster,
+        CasterForward,
+        Target
+    }
+}