feat(backend): 完善 Workflow 与 DeepResearch 的运行链路与持久化能力

功能说明：\n- 重构并增强工作流网关执行链路，支持更完整的 proposal 与 run 调度参数透传\n- 增加 DeepResearch/workflow 运行事件持久化能力并补齐建表 SQL 与查询/保存接口适配\n- 优化 lead agent 与 deep research runner 的中间态处理，增强线程收集与执行链并发控制\n- 调整工作流执行器与任务路由，提升兼容性并完善错误与回放行为\n- 补充回归测试：deep_research 持久化、workflow 并发、定义加载、引擎执行、run 流程等覆盖

offline-backend-20260512/backend/tests/test_workflow_definitions.py

@@ -170,13 +170,17 @@ def test_workflow_http_api_and_coze_compat(monkeypatch: pytest.MonkeyPatch) -> N
     assert published["version_number"] == 1
 
     types = client.get("/api/workflows/node-types").json()
-    assert len(types["nodeTypes"]) == 13
+    # The built-in catalog may grow while preserving the minimum v1 nodes.
+    assert len(types["nodeTypes"]) >= 13
 
     canvas = client.post("/api/workflow_api/canvas", json={"workflowId": wf_id}).json()
     assert canvas["code"] == 0
     workflow_brief = canvas["data"]["workflow"]
     assert workflow_brief["workflow_id"] == wf_id
     assert workflow_brief["is_published"] is True
+    # Coze Playground uses this alongside VCS metadata to decide whether nodes
+    # are draggable. An owned standalone workflow must not open as preview.
+    assert workflow_brief["creator"]["self"] is True
     # Never opened in the Coze editor → built-in start→end canvas fallback.
     assert json.loads(workflow_brief["schema_json"])["nodes"]