feat(workflow): 增加会话级多智能体任务规划运行能力

提交范围聚焦于工作流编排新增：新增 workflow_planning 路由与前后端运行入口（workflow_planning.py、workflow_proposal_planner.py、workflow_deep_research_adapter.py），支持基于会话的提案-规划-执行流程，满足任务驱动式多智能体协作。

完成网关层运行时适配：扩展 workflow_resource_checks、workflow_executor、workflow_runs、workflow_agent_runner 与依赖注入，新增/更新配置（config.yaml、workflow_config），并补充 lead_agent 路径与节点实现，确保 Planner 与普通工作流运行态衔接一致。

补齐持久化与建模：新增 workflow_planning 持久化模块与 MySQL migration（20260831_01_workflow_planning_sessions），注册 SQL 与模型、内存 store，并扩展错误/表达式/validator/节点语义以承载新会话态输入输出。

增强文档与测试：新增会话式多智能体编排中文说明、更新开发文档与 AGENTS 指南、补充 workflow_engine/workflow_runs 回归测试，提高新路径的行为可验证性；同时留存 seed 资产（workflow-planner）便于一体化部署。

offline-backend-20260512/backend/app/gateway/routers/workflow_resources.py

@@ -7,6 +7,7 @@ from typing import Any
 from fastapi import APIRouter, HTTPException, Request
 
 from app.gateway.deps import get_current_user, get_local_provider
+from app.gateway.routers._workflow_planner_seed import WORKFLOW_PLANNER_AGENT_ID
 from deerflow.config.app_config import get_app_config
 from deerflow.persistence.workflows import WorkflowStore
 from deerflow.workflows.schemas import ALL_NODE_TYPES
@@ -22,6 +23,8 @@ _NODE_META: dict[str, dict[str, str]] = {
     "sql_read": {"label": "SQL 只读", "category": "data"},
     "code": {"label": "代码", "category": "data"},
     "transform": {"label": "模板/转换", "category": "data"},
+    "evidence_normalizer": {"label": "证据归一化", "category": "data"},
+    "deep_research_write": {"label": "深度研究报告", "category": "ai"},
     "condition": {"label": "条件", "category": "control"},
     "merge": {"label": "合并", "category": "control"},
     "human_input": {"label": "人工介入", "category": "control"},
@@ -105,6 +108,14 @@ async def list_agent_resources(request: Request) -> dict[str, Any]:
                 rows = await agent_store.list_all()
             else:
                 rows = []
+            # This is a control-plane agent. It plans candidates through the
+            # planning endpoint and must never appear as a draggable worker.
+            rows = [
+                row
+                for row in rows or []
+                if isinstance(row, dict)
+                and str(row.get("id") or row.get("agent_id") or "") != WORKFLOW_PLANNER_AGENT_ID
+            ]
             creator_names = await _resolve_creator_names({str(row["user_id"]) for row in rows or [] if row.get("user_id") is not None})
             agent_ids = [str(row.get("id") or row.get("agent_id") or "") for row in rows or []]
             extras_by_agent: dict[str, dict[str, Any]] = {}