refactor(server): steward 决策链路改用 LangGraph 编排

- 新增 StewardGraphPlannerService，用 LangGraph 状态图编排意图识别→流程判断→模型/规则分支→兜底，替代原 planner 内线性调用
- 新增 StewardGraphRuntimeService 编排运行时决策与槽位决策；StewardActionContracts/Executor 统一动作合约与执行
- steward_intent_agent/application_fact_resolver/runtime_chat 适配图执行器，config 暴露图相关开关
- pyproject/uv.lock 新增 langgraph 依赖
- 新增 graph_planner/graph_runtime/action_executor 测试，更新 intent_agent/planner/fact_resolver/runtime_chat/reimbursement 测试

server/src/app/services/steward_planner_extraction.py

@@ -133,6 +133,7 @@ class StewardPlannerExtractionMixin:
             summary=self._build_task_summary(draft.segment, fields),
             status="needs_confirmation",
             confidence=self._resolve_task_confidence(draft.segment, fields, draft.task_type),
+            requested_action=self._resolve_requested_action(draft.segment),  # type: ignore[arg-type]
             ontology_fields=fields,
             missing_fields=missing_fields,
             confirmation_required=True,
@@ -205,6 +206,15 @@ class StewardPlannerExtractionMixin:
     def _extract_transport_mode(segment: str) -> str:
         return ApplicationFactResolver.extract_transport_mode(segment)
 
+    @staticmethod
+    def _resolve_requested_action(segment: str) -> str:
+        compact = re.sub(r"\s+", "", segment)
+        if re.search(r"直接提交|提交申请|确认提交|提交审批", compact):
+            return "submit"
+        if re.search(r"保存草稿|存草稿|先保存|保存", compact):
+            return "save_draft"
+        return "preview"
+
     @staticmethod
     def _resolve_missing_fields(task_type: str, fields: dict[str, str]) -> list[str]:
         required = ["expense_type", "time_range", "reason"]
@@ -575,4 +585,3 @@ class StewardPlannerExtractionMixin:
     @staticmethod
     def _clean_text(value: Any) -> str:
         return re.sub(r"\s+", " ", str(value or "")).strip()
-