perf(web): PluginGraphPage 替换持续 rAF 循环为按需重绘

移除持续 requestAnimationFrame 循环，改为数据变更 useEffect 触发
单次重绘 + ResizeObserver 监听容器变化，静态页面 CPU 占用大幅降低。

apps/web/src/pages/PluginGraphPage.tsx

@@ -376,15 +376,22 @@ export function PluginGraphPage() {
     }
   }, [canvasSize, selectedCenter, hoverState, token]);
 
-  // ── Animation loop ──
+  // ── On-demand redraw: data changes + resize ──
 
+  // 数据变更时触发单次重绘
   useEffect(() => {
-    const animate = () => {
+    drawGraph();
+  }, [drawGraph]);
+
+  // 容器大小变化时触发重绘
+  useEffect(() => {
+    const container = containerRef.current;
+    if (!container) return;
+    const observer = new ResizeObserver(() => {
       drawGraph();
-      animFrameRef.current = requestAnimationFrame(animate);
-    };
-    animFrameRef.current = requestAnimationFrame(animate);
-    return () => cancelAnimationFrame(animFrameRef.current);
+    });
+    observer.observe(container);
+    return () => observer.disconnect();
   }, [drawGraph]);
 
   // ── Mouse interaction handlers ──