fix(email): wrap root blocks in valid MJML layouts

packages/email-renderer/src/email.ts

@@ -139,6 +139,7 @@ export async function renderEmail(
     direction: options.direction ?? "ltr",
     countdownImageUrl: options.countdownImageUrl,
     brandLinkColor: String(source.root.props.linkColor ?? "#2563eb"),
+    rootBlockIds: Object.values(source.root.slots).flat().map(node => node.id),
   };
   const [htmlResult, textResult, mjmlResult] = await Promise.all([
     renderTree(source, emailKind, registry, { ...base, target: "emailHtml", data: options.variables }),