Next.js page/layout convention exports are in correct file types

A metadata export inside a 'use client' page is one of the most common silent failures in AI-generated Next.js code: the model writes both directives in the same file, Next.js drops the metadata without any warning, and the page ships with no <title> or <meta description>. The same applies to generateStaticParams placed in a component file — it runs nowhere. CWE-489 (Active Debug Code) maps loosely, but the practical harm is SEO blackout and broken static generation — neither of which surfaces in development because the app still renders.

Split 'use client' pages that export metadata into a server wrapper and a client component. Move all convention exports to the server file.

// app/dashboard/page.tsx — server component (no 'use client')
export const metadata = { title: 'Dashboard', description: 'Your overview' }
export { default } from './dashboard-client'

// app/dashboard/dashboard-client.tsx
'use client'
import { useState } from 'react'
export default function Dashboard() {
  const [count, setCount] = useState(0)
  return <div>{count}</div>
}

For dynamic or revalidate found in component files under src/components/, move the export to the page.tsx, layout.tsx, or route.ts that imports the component. Config exports have no effect in component files.