fix(vercel): restore mdx defaults for shiki

Assisted-by: Codex 5.3

Co-authored-by: Claudio Wunder <[email protected]>

Author: cursoragent

packages/platform-vercel/__tests__/next.platform.config.test.mjs

@@ -0,0 +1,13 @@
+import assert from 'node:assert/strict';
+import { describe, it } from 'node:test';
+
+describe('platform-vercel next.platform.config', () => {
+  it('defines shiki mdx defaults for Vercel builds', async () => {
+    const { default: platform } = await import('../next.platform.config.mjs');
+
+    assert.deepEqual(platform.mdx, {
+      wasm: true,
+      twoslash: true,
+    });
+  });
+});

packages/platform-vercel/next.platform.config.mjs

@@ -25,4 +25,10 @@ export default {
     '@platform/analytics': '@node-core/platform-vercel/analytics',
     '@platform/instrumentation': '@node-core/platform-vercel/instrumentation',
   },
+  mdx: {
+    // Vercel supports the fast Oniguruma WASM engine and twoslash transforms,
+    // so keep parity with the default standalone config.
+    wasm: true,
+    twoslash: true,
+  },
 };