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-editor/src/styles/ChunkVisualizer.css

@@ -0,0 +1,139 @@
+.chunk-visualizer {
+    position: absolute;
+    pointer-events: none;
+    z-index: 100;
+}
+
+.chunk-visualizer-overlay {
+    position: absolute;
+    top: 0;
+    left: 0;
+    width: 100%;
+    height: 100%;
+    overflow: hidden;
+}
+
+.chunk-grid-cell {
+    position: absolute;
+    box-sizing: border-box;
+    border: 1px solid rgba(100, 149, 237, 0.3);
+    transition: background-color 0.2s ease;
+}
+
+.chunk-grid-cell.loaded {
+    background-color: rgba(100, 149, 237, 0.1);
+    border-color: rgba(100, 149, 237, 0.5);
+}
+
+.chunk-grid-cell.loading {
+    background-color: rgba(255, 193, 7, 0.2);
+    border-color: rgba(255, 193, 7, 0.6);
+    animation: chunk-loading-pulse 1s ease-in-out infinite;
+}
+
+.chunk-grid-cell.unloading {
+    background-color: rgba(255, 87, 34, 0.2);
+    border-color: rgba(255, 87, 34, 0.5);
+}
+
+.chunk-grid-cell.failed {
+    background-color: rgba(244, 67, 54, 0.2);
+    border-color: rgba(244, 67, 54, 0.6);
+}
+
+.chunk-grid-cell.anchor-chunk {
+    border-color: rgba(76, 175, 80, 0.8);
+    border-width: 2px;
+}
+
+@keyframes chunk-loading-pulse {
+    0%, 100% { opacity: 0.5; }
+    50% { opacity: 1; }
+}
+
+.chunk-coord-label {
+    position: absolute;
+    top: 2px;
+    left: 2px;
+    font-size: 10px;
+    color: rgba(255, 255, 255, 0.6);
+    font-family: monospace;
+    pointer-events: none;
+}
+
+.anchor-marker {
+    position: absolute;
+    width: 12px;
+    height: 12px;
+    border-radius: 50%;
+    background-color: rgba(76, 175, 80, 0.8);
+    border: 2px solid #4caf50;
+    transform: translate(-50%, -50%);
+    z-index: 101;
+}
+
+.anchor-marker::after {
+    content: '';
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    width: 4px;
+    height: 4px;
+    background-color: white;
+    border-radius: 50%;
+    transform: translate(-50%, -50%);
+}
+
+.load-radius-indicator {
+    position: absolute;
+    border: 2px dashed rgba(76, 175, 80, 0.5);
+    border-radius: 4px;
+    pointer-events: none;
+}
+
+.unload-radius-indicator {
+    position: absolute;
+    border: 1px dashed rgba(255, 87, 34, 0.3);
+    border-radius: 4px;
+    pointer-events: none;
+}
+
+.chunk-stats-panel {
+    position: absolute;
+    top: 8px;
+    right: 8px;
+    background: rgba(30, 30, 30, 0.9);
+    border: 1px solid #3e3e42;
+    border-radius: 4px;
+    padding: 8px 12px;
+    font-size: 11px;
+    color: #cccccc;
+    pointer-events: auto;
+    min-width: 140px;
+}
+
+.chunk-stats-panel h4 {
+    margin: 0 0 6px 0;
+    font-size: 12px;
+    color: #ffffff;
+    border-bottom: 1px solid #3e3e42;
+    padding-bottom: 4px;
+}
+
+.chunk-stats-row {
+    display: flex;
+    justify-content: space-between;
+    margin: 2px 0;
+}
+
+.chunk-stats-row .label {
+    color: #888888;
+}
+
+.chunk-stats-row .value {
+    font-family: monospace;
+}
+
+.chunk-stats-row .value.loaded { color: #64b5f6; }
+.chunk-stats-row .value.loading { color: #ffc107; }
+.chunk-stats-row .value.pending { color: #ff9800; }