feat: complete MDX migration, stabilize environment & verify via E2E tests

Former-commit-id: ec3e64156a2e182535cbdcf0d975cd54603a517d

next.config.mjs

@@ -2,7 +2,7 @@ import withMintelConfig from '@mintel/next-config';
 import withBundleAnalyzer from '@next/bundle-analyzer';
 import { withSentryConfig } from '@sentry/nextjs';
 
-import { withPayload } from '@payloadcms/next/withPayload';
+import createMDX from '@next/mdx';
 
 const isProd = process.env.NODE_ENV === 'production';
 /** @type {import('next').NextConfig} */
@@ -20,7 +20,6 @@ const nextConfig = {
       'framer-motion',
       '@/components/ui',
       '@sentry/nextjs',
-      '@payloadcms/richtext-lexical',
       'react-hook-form',
       'zod',
       'date-fns',
@@ -523,7 +522,8 @@ const withAnalyzer = withBundleAnalyzer({
 // withMintelConfig internally sets output:'standalone' and wraps with withSentryConfig.
 // In dev mode, standalone triggers @vercel/nft file tracing on every compile through
 // VirtioFS, which hammers CPU. Strip it for dev.
-let resolvedConfig = withPayload(withAnalyzer(withMintelConfig(nextConfig)));
+const withMDX = createMDX({});
+let resolvedConfig = withMDX(withAnalyzer(withMintelConfig(nextConfig)));
 
 if (!isProd) {
   delete resolvedConfig.output;