Add execution engine and task lifecycle services

tests/integration/test_http_app.py

@@ -28,10 +28,28 @@ def test_post_tasks_creates_planned_task() -> None:
     payload = response.json()
 
     assert response.status_code == 200
-    assert payload["status"] == "planned"
+    assert payload["status"] == "running"
     assert payload["progress"]["total"] == 2
 
 
+def test_cancel_endpoint_marks_task_cancelled() -> None:
+    client = TestClient(app)
+
+    created = client.post(
+        "/tasks",
+        json={
+            "project_id": "default",
+            "goal": "Cancel me",
+            "inputs": {},
+            "execution_mode": "agent_graph",
+        },
+    ).json()
+    response = client.post(f"/tasks/{created['task_id']}/cancel", json={"reason": "stop"})
+
+    assert response.status_code == 200
+    assert response.json()["status"] == "cancelled"
+
+
 def test_worker_registration_is_exposed_via_list_endpoint() -> None:
     client = TestClient(app)