test(ci): add exporter heading levels and a11y typography smoke; update MAIN_PLAN

app/[locale]/page.tsx

@@ -0,0 +1,15 @@
+import Link from 'next/link'
+import { defaultLocale } from '@/lib/i18n/locales'
+
+export default function IndexPage({ params }: { params: { locale: string } }) {
+  const loc = params.locale || defaultLocale
+  return (
+    <main className="p-6">
+      <h1 className="text-2xl font-semibold mb-4">Landing Builder</h1>
+      <p className="mb-4">Start building your landing page.</p>
+      <Link className="text-sky-600 underline" href={`/${loc}/builder`}>
+        Go to Builder
+      </Link>
+    </main>
+  )
+}