feat: 统一 Admin 用户中心 + 修复默认对话记忆存储路径

## 前端
- 新增 AdminUserHub 页面，合并用户管理/审计/记忆三个页面为统一中心（左侧用户列表 + 右侧 Tab）
- 旧三条 admin 路由重定向到新 /admin 路由
- 侧边栏导航菜单合并为单一入口"用户中心"
- memory-settings-page: 默认助手下拉选项传 agent=default（后端识别为全局哨兵）

## 后端
- memory.py: 将 "default" 加入全局哨兵 _GLOBAL_AGENT_VALUES，?agent=default 读全局记忆文件
- memory_middleware.py: _resolve_agent_id() 无 agent 上下文时返回 None，默认对话写入 users/{id}/memory.json
- manager.py: 移除 agent_id or "default" 回退，让 None 透传给 V1 provider
- admin_users.py: Admin 记忆 API 将"默认助手"桶改为读全局文件（agent_id=None）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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

@@ -181,9 +181,10 @@ async def get_user_memory(user_id: str, request: Request) -> AdminMemoryResponse
         # V1 模式：每个桶读 memory.json，内容为 {facts, user, history}
         buckets: list[AdminMemoryBucket] = []
         try:
-            buckets.append(AdminMemoryBucket(name="global", display_name="用户记忆", data=_read_v1_memory_bucket(user_id, None)))
+            buckets.append(AdminMemoryBucket(name="default", display_name="默认助手", data=_read_v1_memory_bucket(user_id, None)))
         except Exception:
-            buckets.append(AdminMemoryBucket(name="global", display_name="用户记忆", data={}))
+            logger.exception("Failed to read V1 global memory for user %s", user_id)
+            buckets.append(AdminMemoryBucket(name="default", display_name="默认助手", data={}))
 
         for agent in owned_agents:
             agent_id: str = agent["id"]
@@ -198,7 +199,7 @@ async def get_user_memory(user_id: str, request: Request) -> AdminMemoryResponse
 
     # V2 模式：读 USER.md / MEMORY.md，内容为 {entries: [...]}
     buckets = [
-        AdminMemoryBucket(name="global", display_name="用户画像", data=_read_memory_bucket(user_id, None))
+        AdminMemoryBucket(name="default", display_name="默认助手", data=_read_memory_bucket(user_id, None))
     ]
     for agent in owned_agents:
         agent_id = agent["id"]

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

@@ -39,7 +39,7 @@ router = APIRouter(prefix="/api", tags=["memory"])
 
 
 # 表示"全局桶 (无 agent)"的 agent 取值。
-_GLOBAL_AGENT_VALUES: frozenset[str] = frozenset({"", "global", "__global__"})
+_GLOBAL_AGENT_VALUES: frozenset[str] = frozenset({"", "global", "__global__", "default"})
 
 
 def _resolve_agent_name(agent: str | None) -> str | None:

offline-backend-20260512/backend/packages/harness/deerflow/agents/memory/manager.py

@@ -288,7 +288,7 @@ def build_memory_manager(
 
     manager.initialize_all(
         user_id=user_id,
-        agent_id=agent_id or "default",
+        agent_id=agent_id,
         thread_id=thread_id,
         base_dir=base_dir,
     )

offline-backend-20260512/backend/packages/harness/deerflow/agents/middlewares/memory_middleware.py

@@ -117,15 +117,18 @@ class MemoryMiddleware(AgentMiddleware[MemoryMiddlewareState]):
         except RuntimeError:
             return None
 
-    def _resolve_agent_id(self, runtime: Runtime | None) -> str:
-        """解析 agent_id;优先 middleware 构造时的 agent_name,再 runtime context。"""
+    def _resolve_agent_id(self, runtime: Runtime | None) -> str | None:
+        """解析 agent_id;优先 middleware 构造时的 agent_name,再 runtime context。
+
+        无 agent 上下文时返回 None，使 V1 记忆存入全局文件（users/{id}/memory.json）。
+        """
         if self._agent_name:
             return self._agent_name
         if runtime is not None and getattr(runtime, "context", None):
             agent_id = runtime.context.get("agent_id")
             if agent_id:
                 return str(agent_id)
-        return "default"
+        return None
 
     # ---- wrap_model_call:Hindsight 动态召回注入 -------------------------