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/SkillProjectile.cs

@@ -0,0 +1,89 @@
+using UnityEngine;
+
+namespace Colosseum.Skills
+{
+    /// <summary>
+    /// 스킬 투사체. 충돌 시 연결된 효과를 적용합니다.
+    /// </summary>
+    [RequireComponent(typeof(Rigidbody))]
+    public class SkillProjectile : MonoBehaviour
+    {
+        [Header("이동 설정")]
+        [Min(0f)] [SerializeField] private float speed = 15f;
+        [Min(0f)] [SerializeField] private float lifetime = 5f;
+
+        [Header("관통 설정")]
+        [SerializeField] private bool penetrate = false;
+        [SerializeField] private int maxPenetration = 1;
+
+        [Header("충돌 이펙트")]
+        [SerializeField] private GameObject hitEffect;
+        [SerializeField] private float hitEffectDuration = 2f;
+
+        private GameObject caster;
+        private SkillEffect sourceEffect;
+        private int penetrationCount;
+        private Rigidbody rb;
+        private bool initialized;
+
+        /// <summary>
+        /// 투사체 초기화
+        /// </summary>
+        public void Initialize(GameObject caster, SkillEffect sourceEffect)
+        {
+            this.caster = caster;
+            this.sourceEffect = sourceEffect;
+            initialized = true;
+
+            rb = GetComponent<Rigidbody>();
+            if (rb != null)
+            {
+                rb.useGravity = false;
+                rb.collisionDetectionMode = CollisionDetectionMode.ContinuousDynamic;
+            }
+        }
+
+        private void Start()
+        {
+            Destroy(gameObject, lifetime);
+        }
+
+        private void FixedUpdate()
+        {
+            if (!initialized || rb == null) return;
+            rb.linearVelocity = transform.forward * speed;
+        }
+
+        private void OnTriggerEnter(Collider other)
+        {
+            if (!initialized || sourceEffect == null) return;
+            if (other.gameObject == caster) return;
+
+            // 유효한 타겟인지 확인
+            if (!sourceEffect.IsValidTarget(caster, other.gameObject))
+                return;
+
+            // 충돌 이펙트
+            if (hitEffect != null)
+            {
+                var effect = Instantiate(hitEffect, transform.position, transform.rotation);
+                Destroy(effect, hitEffectDuration);
+            }
+
+            // 효과 적용
+            sourceEffect.ExecuteOnHit(caster, other.gameObject);
+
+            penetrationCount++;
+
+            if (!penetrate || penetrationCount >= maxPenetration)
+            {
+                Destroy(gameObject);
+            }
+        }
+
+        public void SetDirection(Vector3 direction)
+        {
+            transform.rotation = Quaternion.LookRotation(direction.normalized);
+        }
+    }
+}