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/tests/test_steward_intent_agent.py

@@ -2,6 +2,24 @@ from app.services.steward_intent_agent import (
     STEWARD_INTENT_FUNCTION_NAME,
     StewardIntentAgent,
 )
+from app.schemas.steward import StewardPlanRequest
+
+
+class _NoToolCallRuntimeChatService:
+    def __init__(self) -> None:
+        self.kwargs = {}
+
+    def complete_with_tool_call(self, messages, **kwargs):
+        self.kwargs = kwargs
+
+        class _Result:
+            tool_call = None
+
+            @staticmethod
+            def calls_as_dicts():
+                return []
+
+        return _Result()
 
 
 def test_steward_intent_tool_schema_supports_pending_flow_confirmation() -> None:
@@ -12,9 +30,16 @@ def test_steward_intent_tool_schema_supports_pending_flow_confirmation() -> None
     function_schema = schema["function"]
     assert function_schema["name"] == STEWARD_INTENT_FUNCTION_NAME
     properties = function_schema["parameters"]["properties"]
+    task_schema = properties["tasks"]["items"]
     pending_schema = properties["pending_flow_confirmation"]
     candidate_schema = pending_schema["properties"]["candidate_flows"]["items"]
 
+    assert task_schema["properties"]["requested_action"]["enum"] == [
+        "preview",
+        "save_draft",
+        "submit",
+    ]
+    assert "requested_action" in task_schema["required"]
     assert "pending_flow_confirmation" in properties
     assert pending_schema["properties"]["status"]["enum"] == ["none", "pending"]
     assert candidate_schema["properties"]["flow_id"]["enum"] == [
@@ -28,3 +53,18 @@ def test_steward_intent_tool_schema_supports_pending_flow_confirmation() -> None
         "reason",
         "transport_mode",
     ]
+
+
+def test_steward_intent_agent_uses_ten_second_timeout_and_three_attempts() -> None:
+    runtime_chat = _NoToolCallRuntimeChatService()
+    agent = StewardIntentAgent(runtime_chat)
+
+    agent.detect(
+        StewardPlanRequest(message="2026-02-20 至 2026-02-23，上海出差，火车，保存草稿。"),
+        base_date=__import__("datetime").date(2026, 6, 24),
+        canonical_fields=["expense_type", "time_range", "location", "reason", "transport_mode"],
+    )
+
+    assert runtime_chat.kwargs["timeout_seconds"] == 10
+    assert runtime_chat.kwargs["max_attempts"] == 3
+    assert runtime_chat.kwargs["use_failure_cooldown"] is False