feat: add task duration tracking

tests/tools.test.ts

@@ -113,3 +113,42 @@ test("list is compact and get returns available details for multiple IDs", async
   assert.equal(parsed[1].description, undefined);
   assert.equal(parsed[1].parentId, 1);
 });
+
+test("get_task exposes cumulative timing while list output stays compact", async () => {
+  const startedAt = Date.UTC(2026, 0, 1);
+  let now = startedAt;
+  const harness = registeredTools(new TaskState(() => now));
+  const added = await execute(harness.tools.get("set_tasks"), {
+    mode: "append",
+    tasks: [{ name: "Timed", status: "in-progress" }],
+  });
+  assert.equal(added.content[0].text, "Added 1 task: 1. 0/1 done.");
+  assert.equal(added.details.snapshot.timings[0].activeStartedAt, startedAt);
+
+  now += 65_432;
+  const list = await execute(harness.tools.get("list_task"), {});
+  assert.equal(list.content[0].text, "1 [in-progress] Timed");
+
+  const active = JSON.parse((await execute(harness.tools.get("get_task"), { ids: [1] })).content[0].text);
+  assert.deepEqual(active[0], {
+    id: 1,
+    name: "Timed",
+    status: "in-progress",
+    parentId: null,
+    childrenIds: [],
+    startedAt: new Date(startedAt).toISOString(),
+    durationMs: 65_432,
+  });
+
+  now += 568;
+  const updated = await execute(harness.tools.get("update_task"), {
+    tasks: [{ id: 1, status: "blocked" }],
+  });
+  assert.equal(updated.content[0].text, "Updated 1 task: 1. 0/1 done.");
+
+  now += 10_000;
+  const paused = JSON.parse((await execute(harness.tools.get("get_task"), { ids: [1] })).content[0].text);
+  assert.equal(paused[0].startedAt, new Date(startedAt).toISOString());
+  assert.equal(paused[0].stoppedAt, new Date(startedAt + 66_000).toISOString());
+  assert.equal(paused[0].durationMs, 66_000);
+});