Add recent tag buttons under the tag picker

Under the TAG picker, the timer form shows buttons for the 3 different
tags from the most recent sessions, newest first. A tap selects the
tag. It does not start a session.

The minute buttons move under the DURATION field. They share the column
width, so all six stay on one line on desktop and on mobile.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

tests/recent-tags.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, test } from "bun:test";
+import { recentTags } from "../src/client/recent-tags.ts";
+
+const at = (minute: number, tag: string, deleted = false) => ({ startMs: minute * 60_000, tag, deleted });
+
+describe("recent tags", () => {
+  test("gives the 3 different tags from the most recent sessions, newest first", () => {
+    const records = [at(1, "Read"), at(2, "Study"), at(3, "Gym"), at(4, "Study"), at(5, "Code"), at(6, "Study")];
+    expect(recentTags(records)).toEqual(["Study", "Code", "Gym"]);
+  });
+
+  test("does not depend on the order of the records", () => {
+    expect(recentTags([at(9, "Code"), at(1, "Read"), at(5, "Study")])).toEqual(["Code", "Study", "Read"]);
+  });
+
+  test("ignores deleted sessions", () => {
+    expect(recentTags([at(1, "Read"), at(2, "Study", true)])).toEqual(["Read"]);
+  });
+
+  test("gives fewer tags when there are fewer than 3", () => {
+    expect(recentTags([at(1, "Study"), at(2, "Study")])).toEqual(["Study"]);
+    expect(recentTags([])).toEqual([]);
+  });
+});
+
+test("the timer form puts each row of buttons under its field", async () => {
+  const source = await Bun.file("src/client/main.ts").text();
+  const form = source.slice(source.indexOf('id="timer-tag"'), source.indexOf('data-action="start"'));
+  const tagRow = form.indexOf('data-action="pick-tag"');
+  const durationField = form.indexOf('id="timer-duration"');
+  const minuteRow = form.indexOf('data-action="duration"');
+  expect(tagRow).toBeGreaterThan(-1);
+  expect(tagRow).toBeLessThan(durationField);
+  expect(minuteRow).toBeGreaterThan(durationField);
+});