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/schemas/steward.py

@@ -4,11 +4,11 @@ from typing import Any, Literal
 
 from pydantic import BaseModel, Field
 
-
 StewardTaskType = Literal["expense_application", "reimbursement"]
 StewardAssignedAgent = Literal["application_assistant", "reimbursement_assistant"]
 StewardPlanningSource = Literal["llm_function_call", "rule_fallback"]
 StewardPlanNextAction = Literal["confirm_flow", "confirm_task", "delegate_task", "none"]
+StewardRequestedAction = Literal["preview", "save_draft", "submit"]
 StewardSlotDecisionSource = Literal["llm_function_call", "rule_fallback"]
 StewardSlotNextAction = Literal["ask_user", "render_preview"]
 StewardRuntimeDecisionSource = Literal["llm_function_call", "rule_fallback"]
@@ -22,6 +22,22 @@ StewardRuntimeNextAction = Literal[
     "cancel_current_action",
     "no_op",
 ]
+StewardActionType = Literal[
+    "detect_intent",
+    "fill_application_fields",
+    "build_application_preview",
+    "fill_reimbursement_fields",
+    "build_reimbursement_preview",
+    "validate_required_fields",
+    "run_duplicate_precheck",
+    "save_application_draft",
+    "submit_application",
+    "link_existing_application",
+    "create_reimbursement_draft",
+    "associate_attachments",
+]
+StewardActionStatus = Literal["completed", "planned", "pending_confirmation", "blocked"]
+StewardActionExecutionStatus = Literal["succeeded", "blocked", "needs_confirmation", "failed"]
 StewardTaskStatus = Literal[
     "planned",
     "needs_confirmation",
@@ -58,6 +74,17 @@ class StewardThinkingEvent(BaseModel):
     status: str = Field(default="completed", description="事件状态。")
 
 
+class StewardActionStep(BaseModel):
+    step_id: str = Field(description="动作步骤 ID。")
+    action_type: StewardActionType = Field(description="白名单动作类型。")
+    label: str = Field(description="用户可见动作名称。")
+    target_task_id: str = Field(default="", description="关联的小财管家任务 ID。")
+    status: StewardActionStatus = Field(default="planned", description="动作规划状态。")
+    requires_confirmation: bool = Field(default=False, description="执行前是否需要用户确认。")
+    depends_on: list[str] = Field(default_factory=list, description="前置动作步骤 ID。")
+    payload: dict[str, Any] = Field(default_factory=dict, description="动作执行需要的确定性载荷。")
+
+
 class StewardTask(BaseModel):
     task_id: str = Field(description="小财管家任务 ID。")
     task_type: StewardTaskType = Field(description="任务类型。")
@@ -66,9 +93,11 @@ class StewardTask(BaseModel):
     summary: str = Field(description="任务摘要。")
     status: StewardTaskStatus = Field(default="needs_confirmation", description="任务状态。")
     confidence: float = Field(default=0.0, ge=0.0, le=1.0, description="识别置信度。")
+    requested_action: StewardRequestedAction = Field(default="preview", description="用户希望执行的动作：预览、保存草稿或提交。")
     ontology_fields: dict[str, str] = Field(default_factory=dict, description="归一化后的业务本体字段。")
     missing_fields: list[str] = Field(default_factory=list, description="仍缺失的本体字段。")
     confirmation_required: bool = Field(default=True, description="执行前是否需要用户确认。")
+    action_steps: list[StewardActionStep] = Field(default_factory=list, description="当前任务的白名单动作步骤。")
 
 
 class StewardAttachmentGroup(BaseModel):
@@ -120,6 +149,7 @@ class StewardPlanResponse(BaseModel):
     summary: str = Field(description="计划摘要。")
     thinking_events: list[StewardThinkingEvent] = Field(default_factory=list, description="过程摘要事件。")
     tasks: list[StewardTask] = Field(default_factory=list, description="拆解后的任务。")
+    action_steps: list[StewardActionStep] = Field(default_factory=list, description="本计划的全量白名单动作步骤。")
     attachment_groups: list[StewardAttachmentGroup] = Field(default_factory=list, description="附件归集建议。")
     confirmation_groups: list[StewardConfirmationAction] = Field(default_factory=list, description="等待用户确认的动作。")
     pending_flow_confirmation: StewardPendingFlowConfirmation = Field(
@@ -134,6 +164,30 @@ class StewardPlanResponse(BaseModel):
     )
 
 
+class StewardActionExecuteRequest(BaseModel):
+    action_type: str = Field(description="待执行的白名单动作类型。未知动作会被 executor 阻断。")
+    message: str = Field(default="", description="触发该动作的用户原始话术。")
+    plan_id: str = Field(default="", description="关联的小财管家计划 ID。")
+    conversation_id: str | None = Field(default=None, description="关联会话 ID。")
+    task: StewardTask | None = Field(default=None, description="动作所属任务快照。")
+    action_step: StewardActionStep | None = Field(default=None, description="规划侧生成的动作步骤快照。")
+    confirmed: bool = Field(default=False, description="用户是否已确认执行该动作。")
+    context_json: dict[str, Any] = Field(default_factory=dict, description="前端或运行时补充上下文。")
+    client_trace_id: str = Field(default="", description="前端幂等或追踪 ID。")
+
+
+class StewardActionExecuteResponse(BaseModel):
+    action_type: str = Field(description="实际处理的动作类型。")
+    status: StewardActionExecutionStatus = Field(description="动作执行状态。")
+    execution_source: str = Field(default="langgraph_action", description="执行来源或兜底来源。")
+    fallback_used: bool = Field(default=False, description="是否走了规则兜底执行。")
+    requires_confirmation: bool = Field(default=False, description="是否仍需用户确认。")
+    message: str = Field(description="面向用户展示的执行结果。")
+    blocked_reasons: list[str] = Field(default_factory=list, description="阻断原因。")
+    result_payload: dict[str, Any] = Field(default_factory=dict, description="业务服务返回的结构化结果。")
+    trace: list[dict[str, Any]] = Field(default_factory=list, description="动作执行轨迹。")
+
+
 class StewardSlotOption(BaseModel):
     label: str = Field(description="用户可见选项文案。")
     value: str = Field(description="写回本体字段的选项值。")