feat: mark each speaker with a role icon in the transcript (#5)

src/__tests__/markdown.test.ts

@@ -1,6 +1,8 @@
 import { describe, expect, it } from "vitest";
 import {
+  ASSISTANT_MARKER,
   STREAMING_CURSOR,
+  USER_MARKER,
   buildThreadMarkdown,
   previewText,
   quote,
@@ -44,6 +46,18 @@ describe("buildThreadMarkdown", () => {
     expect(markdown).toContain("4");
   });
 
+  it("marks each speaker with a role icon", () => {
+    const markdown = buildThreadMarkdown([
+      message({ role: "user", text: "q" }),
+      message({ role: "assistant", text: "a" }),
+    ]);
+
+    expect(markdown).toContain(USER_MARKER);
+    expect(markdown).toContain(ASSISTANT_MARKER);
+    // The user marker must not leak onto the answer or vice versa.
+    expect(markdown.indexOf(USER_MARKER)).toBeLessThan(markdown.indexOf(ASSISTANT_MARKER));
+  });
+
   it("keeps the conversation in order", () => {
     const markdown = buildThreadMarkdown([
       message({ id: "a", role: "user", text: "first" }),