feat: newest message first, Raycast-style conversation sidebar (#7)

src/__tests__/utils.test.ts

@@ -1,5 +1,11 @@
 import { describe, expect, it } from "vitest";
-import { errorMessage, formatRelativeTime, titleFromPrompt, truncate } from "../lib/utils";
+import {
+  errorMessage,
+  formatRelativeTime,
+  recencyGroup,
+  titleFromPrompt,
+  truncate,
+} from "../lib/utils";
 
 describe("truncate", () => {
   it("collapses whitespace so list rows never wrap unexpectedly", () => {
@@ -38,6 +44,35 @@ describe("formatRelativeTime", () => {
   });
 });
 
+describe("recencyGroup", () => {
+  // Fixed local noon so the day boundaries are unambiguous on any machine.
+  const now = new Date(2026, 9, 4, 12, 0, 0).getTime();
+  const DAY = 86_400_000;
+
+  it("buckets today", () => {
+    expect(recencyGroup(now - 60_000, now)).toBe("Today");
+  });
+
+  it("buckets yesterday", () => {
+    expect(recencyGroup(new Date(2026, 9, 3, 12, 0, 0).getTime(), now)).toBe("Yesterday");
+  });
+
+  it("buckets the rest of the week", () => {
+    expect(recencyGroup(now - 3 * DAY, now)).toBe("This week");
+    expect(recencyGroup(now - 6 * DAY, now)).toBe("This week");
+  });
+
+  it("buckets anything older", () => {
+    expect(recencyGroup(now - 30 * DAY, now)).toBe("Older");
+  });
+
+  it("does not bucket the small hours of today as yesterday", () => {
+    // Just after midnight is still today, even though it is under 24h ago.
+    const justAfterMidnight = new Date(2026, 9, 4, 0, 5, 0).getTime();
+    expect(recencyGroup(justAfterMidnight, now)).toBe("Today");
+  });
+});
+
 describe("titleFromPrompt", () => {
   it("uses the first non-empty line, stripped of markdown decoration", () => {
     expect(titleFromPrompt("\n\n## How do I deploy?\nmore text", 60)).toBe("How do I deploy?");