refactor: restructure state, routing, and more

js/src/features/network-root.tsx

@@ -0,0 +1,18 @@
+import { useParams } from "react-router-dom";
+import { particlePath } from "@/lib/particle-path";
+import { ParticleListView } from "@/features/particles/particle-list-view";
+
+/**
+ * Route-level component for /:networkId (index).
+ * Shows root-level particles for the selected network.
+ */
+export default function NetworkRoot() {
+  const { networkId } = useParams();
+  const path = particlePath(networkId!, []);
+
+  return (
+    <div className="flex-1 overflow-hidden">
+      <ParticleListView path={path} />
+    </div>
+  );
+}