Full cleanup pass

app/(dev)/layout.tsx

@@ -1,7 +1,10 @@
 import type { ReactNode } from "react";
+import { notFound } from "next/navigation";
 
 // Development-only previews (e.g. `/components-preview`) — no public chrome.
-// Routes here are gated by NODE_ENV checks at the page level.
 export default function DevLayout({ children }: { children: ReactNode }) {
+  if (process.env.NODE_ENV === "production") {
+    notFound();
+  }
   return <main className="flex-1">{children}</main>;
 }