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/Streaming/StreamingBudgetConfigSO.cs

@@ -0,0 +1,71 @@
+using UnityEngine;
+
+namespace BaseGames.World.Streaming
+{
+    /// <summary>
+    /// 流式加载系统的内存与性能预算配置。
+    /// 挂载于 Persistent 场景的 SYS_RoomStreamingManager 对象上，或通过 Inspector 注入。
+    /// 可为不同目标平台（PC / 主机 / 移动端）准备多份配置资产。
+    /// 资产路径：Assets/_Game/Data/Streaming/
+    /// </summary>
+    [CreateAssetMenu(menuName = "BaseGames/World/Streaming/BudgetConfig")]
+    public class StreamingBudgetConfigSO : ScriptableObject
+    {
+        [Header("内存与容量")]
+
+        [Tooltip("同时保持 Dormant 状态的最大房间数量（不含当前 Active 房间）。\n" +
+                 "超出此限制后，LRU 策略将卸载距离最远、最久未访问的 Dormant 房间。")]
+        [Min(1)]
+        public int MaxDormantRooms = 6;
+
+        [Tooltip("房间资产内存上限（MB）。仅用于超出时触发 LRU 卸载的第二道保障检查。\n" +
+                 "需在编辑器 Profiler 中测量各房间实际内存后填入估算值。")]
+        [Min(64)]
+        public int MaxMemoryMB = 300;
+
+        [Header("加载控制")]
+
+        [Tooltip("同时进行的 Addressables 加载操作数量上限。\n" +
+                 "过高会导致 I/O 竞争和帧率波动，建议 1-2。")]
+        [Range(1, 4)]
+        public int MaxConcurrentLoads = 2;
+
+        [Tooltip("预加载的邻居跳数。\n" +
+                 "1 = 仅预加载直接相邻出口的房间；2 = 再加载邻居的邻居。\n" +
+                 "值越高预加载越激进，内存压力越大。")]
+        [Range(1, 3)]
+        public int PreloadLookaheadHops = 2;
+
+        [Header("激活与冷却")]
+
+        [Tooltip("玩家离开房间后，延迟多少秒才将该房间转为 Dormant/Unloaded。\n" +
+                 "防止来回反复时频繁卸载重载。推荐 5-10 s。")]
+        [Min(0f)]
+        public float CoolingDuration = 6f;
+
+        [Tooltip("房间 Activate 时每帧最多激活的 IRoomLifecycle 数量，分帧避免 CPU 峰值。")]
+        [Min(1)]
+        public int LifecycleActivatePerFrame = 8;
+
+        [Header("AtmosphericFade 演出")]
+
+        [Tooltip("AtmosphericFade 过渡的淡出时长（秒）。")]
+        [Range(0.1f, 1f)]
+        public float AtmosphericFadeOutDuration = 0.25f;
+
+        [Tooltip("AtmosphericFade 过渡的淡入时长（秒）。")]
+        [Range(0.1f, 1f)]
+        public float AtmosphericFadeInDuration = 0.3f;
+
+        [Tooltip("AtmosphericFade 过渡中，区域名称文本显示的最短持续时间（秒）。")]
+        [Range(0.5f, 3f)]
+        public float RegionNameDisplayDuration = 1.2f;
+
+        [Header("Seamless 过渡等待")]
+
+        [Tooltip("Seamless 过渡等待目标房间预加载完成的最长时间（秒）。\n" +
+                 "超时后放弃本次切换，玩家可再次触发（届时房间通常已就绪）。")]
+        [Range(2f, 30f)]
+        public float SeamlessWaitTimeout = 10f;
+    }
+}