feat(email-renderer): render countdown images across email targets

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

@@ -56,6 +56,20 @@ const document: BlockDocument = {
 };
 
 describe("email renderer", () => {
+  test("countdown URLs are derived for HTML AMP and MJML without mutating the document", async () => {
+    const draft = structuredClone(document);
+    draft.root.slots.content[0]!.slots.content = [{id:"timer",type:"content.countdown",version:1,props:{label:"Offer ends",deadline:"2026-10-01T00:00:00Z",fallback:"Offer ended"},styles:{},slots:{}}];
+    const before = JSON.stringify(draft);
+    const result = await renderEmail(draft, {amp:true,mjml:true,countdownImageUrl:"https://email.example.com/api/countdown"});
+    expect(result.ok).toBe(true);
+    if (!result.ok) return;
+    const image = "https://email.example.com/api/countdown?deadline=1790812800000";
+    expect(result.value.parts.html.content).toContain(image);
+    expect(result.value.parts.amp?.content).toContain(image);
+    expect(result.value.exports?.mjml).toContain(image);
+    expect(JSON.stringify(draft)).toBe(before);
+    expect((await renderEmail(draft, {countdownImageUrl:"javascript:alert(1)"})).ok).toBe(false);
+  });
   test("content inherits the selected brand font instead of overriding it", async () => {
     const branded = structuredClone(document);
     branded.root.props.fontFamily = "Georgia, serif";