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/World/RoomTransition.cs

@@ -25,9 +25,11 @@ namespace BaseGames.World
         [SerializeField] private string _targetTransitionId;   // 目标房间出生点 ID
 
         [Header("过渡类型")]
-        [Tooltip("Room：极短淡出，无加载画面，相邻房间边界专用。\n" +
-                 "Scene：完整淡出 + 加载画面，大区域/地图间切换专用。")]
-        [SerializeField] private TransitionType _transitionType = TransitionType.Room;
+        [Tooltip("Seamless：无缝切换，流式系统标准选项，绝大多数房间门使用此类型。\n" +
+                 "AtmosphericFade：短暂淡出 + 区域名提示，适合跨大区域边界。\n" +
+                 "Room：极短淡出，不走流式系统（仅用于非流式独立场景切换）。\n" +
+                 "Scene：完整淡出 + 加载画面，大区域/地图间传送专用。")]
+        [SerializeField] private TransitionType _transitionType = TransitionType.Seamless;
 
         [Header("触发方式")]
         [SerializeField] private bool _autoTrigger = true;     // true = 玩家进入触发器自动触发