feat(world-streaming): 添加世界流式加载系统 (#288)

实现基于区块的世界流式加载系统，支持开放世界游戏：

运行时包 (@esengine/world-streaming):
- ChunkComponent: 区块实体组件，包含坐标、边界、状态
- StreamingAnchorComponent: 流式锚点组件（玩家/摄像机）
- ChunkLoaderComponent: 流式加载配置组件
- ChunkStreamingSystem: 区块加载/卸载调度系统
- ChunkCullingSystem: 区块可见性剔除系统
- ChunkManager: 区块生命周期管理服务
- SpatialHashGrid: 空间哈希网格
- ChunkSerializer: 区块序列化

编辑器包 (@esengine/world-streaming-editor):
- ChunkVisualizer: 区块可视化覆盖层
- ChunkLoaderInspectorProvider: 区块加载器检视器
- StreamingAnchorInspectorProvider: 流式锚点检视器
- WorldStreamingPlugin: 完整插件导出

packages/world-streaming/src/systems/ChunkCullingSystem.ts

@@ -0,0 +1,108 @@
+import { EntitySystem, Matcher, ECSSystem } from '@esengine/ecs-framework';
+import type { Entity } from '@esengine/ecs-framework';
+import { ChunkComponent } from '../components/ChunkComponent';
+import { EChunkState } from '../types';
+
+/**
+ * 区块裁剪系统
+ *
+ * Handles visibility culling for chunk entities.
+ *
+ * 处理区块实体的可见性裁剪。
+ */
+@ECSSystem('ChunkCulling', { updateOrder: -40 })
+export class ChunkCullingSystem extends EntitySystem {
+    private _viewMinX: number = 0;
+    private _viewMinY: number = 0;
+    private _viewMaxX: number = 1920;
+    private _viewMaxY: number = 1080;
+    private _padding: number = 100;
+
+    constructor() {
+        super(Matcher.all(ChunkComponent));
+    }
+
+    /**
+     * 设置视口边界
+     *
+     * Set viewport bounds for culling.
+     */
+    setViewBounds(minX: number, minY: number, maxX: number, maxY: number): void {
+        this._viewMinX = minX;
+        this._viewMinY = minY;
+        this._viewMaxX = maxX;
+        this._viewMaxY = maxY;
+    }
+
+    /**
+     * 设置裁剪边距
+     *
+     * Set padding for culling bounds.
+     */
+    setPadding(padding: number): void {
+        this._padding = padding;
+    }
+
+    protected process(entities: readonly Entity[]): void {
+        const cullMinX = this._viewMinX - this._padding;
+        const cullMinY = this._viewMinY - this._padding;
+        const cullMaxX = this._viewMaxX + this._padding;
+        const cullMaxY = this._viewMaxY + this._padding;
+
+        for (const entity of entities) {
+            const chunk = entity.getComponent(ChunkComponent);
+            if (!chunk) continue;
+
+            if (chunk.state !== EChunkState.Loaded) continue;
+
+            const bounds = chunk.bounds;
+            const isVisible = this.boundsIntersect(
+                bounds.minX,
+                bounds.minY,
+                bounds.maxX,
+                bounds.maxY,
+                cullMinX,
+                cullMinY,
+                cullMaxX,
+                cullMaxY
+            );
+
+            entity.enabled = isVisible;
+        }
+    }
+
+    /**
+     * 检查边界是否相交
+     *
+     * Check if two axis-aligned bounds intersect.
+     */
+    private boundsIntersect(
+        aMinX: number,
+        aMinY: number,
+        aMaxX: number,
+        aMaxY: number,
+        bMinX: number,
+        bMinY: number,
+        bMaxX: number,
+        bMaxY: number
+    ): boolean {
+        return aMinX < bMaxX && aMaxX > bMinX && aMinY < bMaxY && aMaxY > bMinY;
+    }
+
+    /**
+     * 更新视口（从相机）
+     *
+     * Update viewport from camera position and size.
+     */
+    updateFromCamera(cameraX: number, cameraY: number, viewWidth: number, viewHeight: number): void {
+        const halfWidth = viewWidth * 0.5;
+        const halfHeight = viewHeight * 0.5;
+
+        this.setViewBounds(
+            cameraX - halfWidth,
+            cameraY - halfHeight,
+            cameraX + halfWidth,
+            cameraY + halfHeight
+        );
+    }
+}