fix(email): validate MJML before exposing exports

packages/email-renderer/src/email.ts

@@ -13,6 +13,7 @@ import {
   type Result,
 } from "@wrnexus/blocks";
 import { emailCoreBlocks, ampLayoutCss } from "./blocks.ts";
+import { validateMjml } from "./mjml.ts";
 
 interface AmpValidationError {
   severity: string;
@@ -168,7 +169,13 @@ export async function renderEmail(
     warnings,
     assets: [],
   };
-  if (mjmlResult?.ok) bundle.exports = { mjml: mjmlResult.value.content };
+  if (mjmlResult?.ok) {
+    const diagnostics = await validateMjml(mjmlResult.value.content);
+    if (!diagnostics.length) bundle.exports = { mjml: mjmlResult.value.content };
+    else warnings.push(...diagnostics.map(diagnostic => ({ ...diagnostic, severity: "warning" as const })));
+  } else if (mjmlResult) {
+    warnings.push(...mjmlResult.errors.map(diagnostic => ({ ...diagnostic, severity: "warning" as const })));
+  }
   if (options.amp) {
     const amp = await renderTree(source, emailKind, registry, { ...base, target: "ampEmail", data: options.variables });
     if (amp.ok) {