feat(enemy): 目标点吸附统一处理导航宽度,Waypoint 不再卡崖边

将"角色导航宽度"收口到导航执行层单一入口,意图层(Locomotion/AI)只递原始目标、不再感知身体尺寸:

- NavAgent 新增 TryGetStandablePointNear:把世界点映射到最近可行走段并按 endMargin 内缩两端(与 SetRandomDestinationOnCurrentSegment 同源)
- EnemyNavAgent 新增 ResolveStandablePoint,以 EnemyMovement.EdgeSafeMargin(半宽+落崖余量)为唯一宽度真源;加 _goalMapSearchRadius
- IPathAgent 暴露 ResolveStandablePoint;FlyingDirectNavigator 原样返回(飞行无崖沿约束),NullPathAgent 空实现
- EnemyLocomotion Waypoint 分支改用吸附后的可达点做移动与到达判定,修复路点摆在空中/崖外时永不到达而卡死;吸附失败显式报错暴露误配,不静默兜底

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

Assets/PathBerserker2d/Scripts/PathBerserker2d/NavAgent/NavAgent.cs

@@ -620,6 +620,33 @@ namespace PathBerserker2d
             return PathTo(goal);
         }
 
+        // [项目新增] 目标点吸附：把任意世界点映射到最近的、agent 容身得下的可行走段上，再按 endMargin
+        // 从段两端内缩，得到"身体真正站得住"的世界点(避免落在角色宽度站不住的崖沿被移动层夹停)。
+        // 与 SetRandomDestinationOnCurrentSegment 同源：endMargin 传 agent 半宽 + 落崖检测余量。
+        // 段短于 2*endMargin → 退化到中点。searchRadius 内映射不到任何段(目标离导航面太远)时返回 false。
+        /// <summary>
+        /// Maps <paramref name="worldTarget"/> to the nearest walkable segment the agent fits on,
+        /// then insets by <paramref name="endMargin"/> from BOTH segment ends so the returned point is
+        /// one a bodied agent can actually stand on (not clamped at a ledge). A segment shorter than
+        /// 2*endMargin degenerates to its midpoint. Returns false (and echoes worldTarget) if nothing
+        /// maps within <paramref name="searchRadius"/>.
+        /// </summary>
+        public bool TryGetStandablePointNear(Vector2 worldTarget, float searchRadius, float endMargin, out Vector2 standable)
+        {
+            if (!PBWorld.TryMapPoint(worldTarget, searchRadius, this, out var ptr))
+            {
+                standable = worldTarget;
+                return false;
+            }
+
+            var cluster = ptr.cluster;
+            float len = cluster.Length;
+            float m = Mathf.Clamp(endMargin, 0f, len * 0.5f); // 段太短 → 退化到中点
+            float t = Mathf.Clamp(ptr.t, m, len - m);
+            standable = cluster.owner.LocalToWorld.MultiplyPoint3x4(cluster.GetPositionAlongSegment(t));
+            return true;
+        }
+
 
         /// <summary>
         /// If you implement link traversal yourself, call this to complete a link traversal.