feat: 管理面板补齐(RAG导入/记忆添加/会话接history/诚实表述) + design/16 §4.6 IM多会话隔离+第三方身份+黑白名单

agent-98 面板批次:
- 会话管理面板改接 history.ListSessions(主web+次级) + 新建次级会话按钮
- 记忆面板手动添加入口 POST /admin/memories(owner)
- 知识库真正实现 IndexDocument(分块+落projectindex) + POST /admin/rag 导入端点
- 三面板空态诚实表述(去除'后端M10+提供')
- RAG嵌入降级到keyword/line(无直属embedder,不伪造语义,符合红线)

agent-99 design/16 §4.6:
- model.Message.SenderName + 迁移0006 sender_name 列
- 第三方身份边界: session.ResolveActor判定(非LLM猜) + [第三方·昵称]前缀(不改源content)
- 群聊/陌生人落独立sess-xxx(persistIsolated),不写主会话,不广播
- 黑/白名单(allowGroups/denyGroups/allowUsers/denyUsers)最前拦截,不进LLM
- 多账号 CHANNELS_JSON 配置 + 每平台多实例
- 管理只读 GET /admin/channels/{platform}/messages(该平台非主人消息流)

实机验证(JWT): 会话管理返回主会话web / 记忆添加成功 / RAG导入documents非空+Cyrene命中; 后端build/vet/test全绿 + 前端build绿

internal/services/gateway/admin.go

@@ -96,8 +96,16 @@ func (s *Server) adminListPersonas(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, s.collectPersonas())
 }
 
-// adminListSessions lists channel sessions (admin read).
+// adminListSessions lists the persistent chat-history sessions (main + sub) when a
+// history store is wired, otherwise falls back to the channel-session view. It is
+// the admin counterpart of handleListSessions: the panel shows the real main and
+// secondary sessions (design/16 §2) rather than stale channel-session rows, and
+// the fallback keeps the pre-design/16 contract for servers built without history.
 func (s *Server) adminListSessions(w http.ResponseWriter, r *http.Request) {
+	if s.history != nil {
+		s.handleHistorySessions(w, r)
+		return
+	}
 	writeJSON(w, http.StatusOK, s.collectSessions(r.Context()))
 }