fix(email-renderer): constrain images to available content width

packages/email-renderer/test/marketing-images.test.ts

@@ -54,6 +54,7 @@ test("product and RSS images survive HTML, AMP and strict MJML exports", async (
     const result = await renderEmail(document(type, props), { amp: true, mjml: true });
     expect(result.ok).toBe(true);
     if (!result.ok) continue;
+    expect(result.value.parts.html.content).toContain('width:100%;max-width:320px;');
     for (const output of [
       result.value.parts.html.content,
       result.value.parts.amp?.content,