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/Map/MapRoomDataSO.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Linq;
 using UnityEngine;
+using BaseGames.Core.Events;
 
 namespace BaseGames.World.Map
 {
@@ -32,6 +33,13 @@ namespace BaseGames.World.Map
         public bool       IsSavePoint;
         public bool       IsShop;
         public Sprite     MapIconOverride;  // null = 按 isXxx 自动选择图标
+
+        [Header("流式加载")]
+        [Tooltip("此房间场景资产的预估内存（KB）。\n" +
+                 "在 Profiler 中测量场景实际内存后填入，供流式管理器执行内存预算检查使用。\n" +
+                 "建议在关卡内容基本定型后更新此值。0 = 未填写，将跳过内存预算检查。")]
+        [Min(0)]
+        public int EstimatedMemoryKB;
     }
 
     [Serializable]
@@ -40,6 +48,11 @@ namespace BaseGames.World.Map
         public string       TargetRoomId;   // 连接的目标房间 ID
         public Vector2Int   ExitGridPos;    // 出口在格子地图上的位置
         public ExitDirection Direction;     // 出口方向
+
+        [Tooltip("此出口触发的过渡类型。\n" +
+                 "Seamless：无缝切换（同区域相邻房间首选）；\n" +
+                 "AtmosphericFade：短暂淡出 + 区域名提示（跨大区域边界首选）。")]
+        public TransitionType PreferredTransitionType;
     }
 
     public enum ExitDirection { Up, Down, Left, Right }
@@ -61,8 +74,11 @@ namespace BaseGames.World.Map
         public MapRoomDataSO GetRoom(string roomId)
         {
             if (_index == null)
+            {
+                if (AllRooms == null) return null;
                 _index = AllRooms.Where(r => r != null)
                                  .ToDictionary(r => r.RoomId);
+            }
             _index.TryGetValue(roomId, out var r);
             return r;
         }