perf: 探索图减少卡顿(数据未变不重建 + 只渲染可见节点)

- graph-tab:轮询按签名判重,图数据无变化时跳过 setState,避免整图重建;
  拖动不再被 20s 轮询打断
- ExplorationGraph:ReactFlow 加 onlyRenderVisibleElements,屏幕外节点不渲染

web/src/components/exploration-graph.tsx

@@ -444,6 +444,7 @@ function ExplorationGraphInner({
         fitView
         fitViewOptions={{ padding: 0.2 }}
         proOptions={{ hideAttribution: true }}
+        onlyRenderVisibleElements
         minZoom={0.1}
         className="!bg-[#f0f2f7] dark:!bg-neutral-950"
       >