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/AI/BD_BossPhaseTransition.cs

@@ -0,0 +1,54 @@
+#if GRAPH_DESIGNER
+using UnityEngine;
+using Opsive.BehaviorDesigner.Runtime.Tasks;
+using Opsive.BehaviorDesigner.Runtime.Tasks.Actions;
+using BaseGames.Enemies;
+
+namespace BaseGames.Enemies.AI
+{
+    /// <summary>
+    /// BD Action：启动 Boss 阶段过渡演出（无敌帧 + 可选定格），等待过渡完成后返回 Success。
+    ///
+    /// 返回 Running：过渡演出进行中（BossBase.IsPhaseTransitioning = true）。
+    /// 返回 Success：过渡完成，已切换到目标阶段。
+    /// 返回 Failure：BossBase 组件不存在。
+    ///
+    /// 典型 BT 用法：
+    ///   Sequence [ BD_IsHPBelow(0.5) → BD_BossPhaseTransition(Phase=1, Duration=1.5) → ... ]
+    /// </summary>
+    [TaskName("Boss Phase Transition")]
+    [TaskCategory("BaseGames/Enemy/Boss")]
+    [TaskDescription("触发 Boss 阶段过渡演出（无敌 + 动画 + 广播事件）")]
+    public class BD_BossPhaseTransition : Action
+    {
+        [Tooltip("切换到的目标阶段索引")]
+        [SerializeField] private int m_TargetPhase = 1;
+
+        [Tooltip("无敌帧 + 过渡演出持续时间（秒）")]
+        [SerializeField, Min(0f)] private float m_InvincibleDuration = 1.5f;
+
+        private BossBase _boss;
+        private bool     _started;
+
+        public override void OnAwake() => _boss = GetComponent<BossBase>();
+
+        public override void OnStart()
+        {
+            _started = false;
+        }
+
+        public override TaskStatus OnUpdate()
+        {
+            if (_boss == null) return TaskStatus.Failure;
+
+            if (!_started)
+            {
+                _boss.BeginPhaseTransition(m_TargetPhase, m_InvincibleDuration);
+                _started = true;
+            }
+
+            return _boss.IsPhaseTransitioning ? TaskStatus.Running : TaskStatus.Success;
+        }
+    }
+}
+#endif