feat: Implement Room Streaming System

- Add RoomStreamingManager to manage room loading and unloading based on player proximity.
- Create StreamingBudgetConfigSO for memory and performance budgeting of the streaming system.
- Introduce TransitionDirector to handle seamless and atmospheric fade transitions between rooms.
- Develop WorldGraph to represent room connectivity and facilitate neighbor queries and distance calculations.
- Implement RoomNode and RoomEdge classes to structure room data and connections.

Assets/_Game/Scripts/Enemies/AiPhase.cs

@@ -0,0 +1,45 @@
+namespace BaseGames.Enemies
+{
+    /// <summary>
+    /// 敌人 AI 行为阶段枚举（独立于 EnemyStateType 的物理/战斗状态）。
+    ///
+    /// 两套状态正交关系：
+    /// - <see cref="EnemyStateType"/>：受击/击飞/死亡等物理事件驱动的瞬时状态。
+    /// - <see cref="AiPhase"/>：行为树主动切换的持续阶段，反映 AI 当前的战术意图。
+    ///
+    /// 典型切换路径：
+    /// <code>
+    /// Idle / Patrol
+    ///   → [感知触发] → Alert（短暂警觉动作）
+    ///   → Chase（追击）
+    ///   → Combat（攻击范围内）
+    ///     ↓ 丢失视线超时
+    ///   → Investigate（前往最后可见位置搜查）
+    ///     ↓ 搜查完成或超出范围
+    ///   → ReturnHome（归位）→ Patrol
+    /// </code>
+    /// </summary>
+    public enum AiPhase
+    {
+        /// <summary>未激活，静止或播放待机循环动画。</summary>
+        Idle,
+
+        /// <summary>沿路点或随机目的地正常巡逻，无感知威胁。</summary>
+        Patrol,
+
+        /// <summary>感知到威胁后的短暂警觉过渡阶段，通常播放抬头/发现动作后进入 Chase。</summary>
+        Alert,
+
+        /// <summary>全力追击玩家，使用奔跑速度。</summary>
+        Chase,
+
+        /// <summary>玩家在攻击距离内，准备或正在执行攻击。</summary>
+        Combat,
+
+        /// <summary>丢失目标后前往最后可见坐标搜查，若无发现则切 ReturnHome 或 Patrol。</summary>
+        Investigate,
+
+        /// <summary>超出追击范围或搜查结束后归位到初始位置。</summary>
+        ReturnHome,
+    }
+}