refactor: unify workflow runtime boundary

tests/test_workflow_runtime_facade.py

@@ -0,0 +1,29 @@
+"""工作流运行时 Application Facade 回归。"""
+
+import pytest
+
+from app.application import workflow as workflow_application
+
+
+def test_workflow_runtime_facade_preserves_registered_identity(monkeypatch) -> None:
+    """Application Facade 必须返回组合根登记的同一个运行时对象。"""
+    runtime = object()
+    monkeypatch.setattr(
+        workflow_application,
+        "_workflow_runtime_provider",
+        lambda: runtime,
+    )
+
+    assert workflow_application.get_workflow_manager() is runtime
+
+
+def test_workflow_runtime_facade_fails_before_composition(monkeypatch) -> None:
+    """未装配时不得隐式创建第二个 WorkFlowManager Singleton。"""
+    monkeypatch.setattr(
+        workflow_application,
+        "_workflow_runtime_provider",
+        workflow_application._unconfigured_workflow_runtime,
+    )
+
+    with pytest.raises(RuntimeError, match="工作流运行时尚未由启动组合根装配"):
+        workflow_application.get_workflow_manager()