fix(email): inherit button brand colors across render targets

packages/email-renderer/test/button-brand.test.ts

@@ -0,0 +1,26 @@
+import { expect, test } from "bun:test";
+import type { BlockDocument } from "@wrnexus/blocks";
+import { renderEmail, validateMjml } from "../src/index.ts";
+
+test("button background inherits brand color with explicit semantic overrides across formats", async () => {
+  for (const override of [undefined, "#aabbcc"]) {
+    const document: BlockDocument = {
+      schemaVersion: 1, kind: "email", meta: { subject: "Brand", lang: "en" }, theme: { tokens: {} },
+      root: { id: "root", type: "layout.email-document", version: 1, props: { linkColor: "#125634" }, styles: {}, slots: {
+        content: [{ id: "button", type: "content.button", version: 1, props: { label: "Act", href: "https://example.com" }, styles: override ? { backgroundColor: { base: override } } : {}, slots: {} }],
+      } },
+    };
+    document.root.slots.content = [{ id: "section", type: "layout.section", version: 1, props: {}, styles: {}, slots: { content: document.root.slots.content } }];
+    const before = structuredClone(document);
+    const rendered = await renderEmail(document, { amp: true, mjml: true, ampValidationTimeoutMs: 10000 });
+    expect(rendered.ok).toBe(true);
+    if (!rendered.ok) return;
+    const color = override ?? "#125634";
+    expect(rendered.value.parts.html.content).toContain(`bgcolor="${color}"`);
+    expect(rendered.value.parts.amp?.validation.valid).toBe(true);
+    expect(rendered.value.parts.amp?.content).toContain(`background-color:${color}`);
+    expect(rendered.value.exports?.mjml).toContain(`background-color="${color}"`);
+    expect(await validateMjml(rendered.value.exports!.mjml!)).toEqual([]);
+    expect(document).toEqual(before);
+  }
+});