feat(orchestrator): pool 异步化（ProcessPoolExecutor spawn + stage 追踪）

tests/orchestrator/test_pool.py

@@ -59,4 +59,36 @@ class TestTaskPool:
         task2 = pool.submit(task_id="test_2", task_type="test")
         assert len(pool._tasks) == 2
         assert pool.get_status("test_1") == TaskState.PENDING
-        assert pool.get_status("test_2") == TaskState.PENDING
+        assert pool.get_status("test_2") == TaskState.PENDING
+
+
+class TestTaskPoolStageAndAsync:
+    """Test TaskPool stage tracking and async execution (Task 3)"""
+
+    def test_task_has_stage_field(self):
+        """Test Task has stage field with default empty string"""
+        from sanguo_orchestrator.task import Task
+        t = Task(task_id="t1", task_type="cta")
+        assert t.stage == ""
+
+    def test_pool_submit_work_returns_future(self):
+        """Test submit_work() returns Future from executor"""
+        from unittest.mock import MagicMock
+        from sanguo_orchestrator.pool import TaskPool
+        pool = TaskPool(max_workers=2)
+        pool.executor = MagicMock()  # mock executor to avoid spawning real processes
+        mock_future = MagicMock()
+        pool.executor.submit.return_value = mock_future
+        fut = pool.submit_work("t1", func=lambda: 1)
+        assert fut is mock_future
+        pool.executor.submit.assert_called_once()
+
+    def test_pool_update_and_get_stage(self):
+        """Test update_stage() and get_stage() methods"""
+        from sanguo_orchestrator.pool import TaskPool
+        from sanguo_orchestrator.task import Task
+        pool = TaskPool(max_workers=2)
+        pool.submit("t1", "cta")
+        pool.update_stage("t1", "回测中")
+        assert pool.get_stage("t1") == "回测中"
+        assert pool.get_task("t1").stage == "回测中"