Split optional routes and editing dialogs from initial browser code

src/components/design-system/deferred.tsx

@@ -0,0 +1,9 @@
+import { lazy, Suspense, type ComponentProps, type ComponentType } from "react";
+
+/** Keep the surrounding workspace usable while an optional surface loads. */
+export function deferred<Component extends ComponentType<any>>(load: () => Promise<Component>) {
+  const Surface = lazy(async () => ({ default: await load() })) as ComponentType<ComponentProps<Component>>;
+  return function Deferred(props: ComponentProps<Component>) {
+    return <Suspense fallback={<p className="ds-supporting-copy" role="status">Loading…</p>}><Surface {...props} /></Suspense>;
+  };
+}