root = Card([header, description, form])
header = CardHeader("Weekly Product Digest", "Curated insights delivered every Monday")
description = TextContent("Get one concise email each week with the top product launches, feature deep-dives, and industry trends — no fluff, just signal.")
form = Form("newsletter-signup", formButtons, [emailField])
formButtons = Buttons([submitBtn], "row")
submitBtn = Button("Subscribe", { type: "continue_conversation", context: "User subscribed to weekly product newsletter" }, "primary")
emailField = FormControl("Email Address", emailInput, "We respect your inbox. Unsubscribe anytime.")
emailInput = Input("email", "you@example.com", "email", { required: true, email: true })