rnxcmkidd: Add the viewport-fit bento shell and a dev feed preview with fixtures

src/app/dev/feed/page.tsx

@@ -0,0 +1,11 @@
+// Dev-only preview of the signed-in feed shell with fixture data (no Minnect
+// login, no network). Not linked from the app and returns 404 in production.
+import { notFound } from "next/navigation";
+import { FeedPreview } from "@/dev/FeedPreview";
+
+export const metadata = { title: "Feed (dev)" };
+
+export default function FeedDevPage() {
+  if (process.env.NODE_ENV === "production") notFound();
+  return <FeedPreview />;
+}