fix(nav): 修复 nav 寻路核心用法——重寻路防抖 + allowCloseEnoughPath

根因1: PathBerserker2d NavAgent.UpdatePath 明确禁止每帧调用(路径计算跨帧,每帧重启则永不完成、
agent永不移动),而追击每帧 MoveTo→RequestMoveTo→UpdatePath。修: EnemyNavAgent.RequestMoveTo
加防抖(目标位移阈值0.5m + 最小间隔0.25s),让路径算完并跟随;StopNavigation 复位。
根因2: NavAgent.allowCloseEnoughPath 默认false→追击玩家(常不在导航段上)寻路直接失败。
修: 脚手架(4个PlaceExxx)+E001 prefab 设为 true(寻路到最近可达点)。
验证: 敌人 nav 巡逻/追击已能真正跟随路径移动(following=True)。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Game/Prefabs/Enemies/E001/ENM_CaoZhi.prefab

@@ -384,7 +384,7 @@ MonoBehaviour:
   - 1
   - 1
   - 1
-  allowCloseEnoughPath: 0
+  allowCloseEnoughPath: 1
   movementSpeed: 5
   cornerSpeed: 100
   jumpSpeed: 5
@@ -436,6 +436,8 @@ MonoBehaviour:
   _groundMask:
     serializedVersion: 2
     m_Bits: 4294967295
+  _repathTargetThreshold: 0.5
+  _repathMinInterval: 0.25
 --- !u!114 &3225188436228842581
 MonoBehaviour:
   m_ObjectHideFlags: 0