feat: 多功能升级 — 流式逐字渲染、对话缓存、会话组织优化、记忆管理修复、性能仪表盘

- 前端消息流式逐字渲染 (AI-Core ChatStream → SSE → Gateway → WebSocket stream_chunk → fadeInUp + cursorBlink)
- 后端对话缓存 (conversationCache sync.Map, GET /sessions/:id/messages)
- 前端侧边栏历史多轮对话显示
- DevTools 性能监控图标移至首页仪表盘
- DevTools 用户记忆查询/删减功能修复 (补全 DELETE 数据链路)
- 后端和 DevTools 按用户分类组织实时活动会话 (map[userID]map[sessionID]*Client)
- 新增 docs/api-reference/ 路由参考文档
- 新增 docs/message-flow-architecture.md 消息链路架构文档

frontend/web/src/components/layout/Sidebar.tsx

@@ -1,6 +1,5 @@
 import { useSession } from '@/hooks/useSession';
 import { useSessionStore } from '@/store/sessionStore';
-import { useEffect } from 'react';
 import { CyreneAvatar } from '@/components/persona/CyreneAvatar';
 
 interface SidebarProps {
@@ -8,20 +7,51 @@ interface SidebarProps {
 }
 
 export function Sidebar({ onClose }: SidebarProps) {
-  const { sessions, currentSessionId, loadSessions, createSession, deleteSession, setCurrentSession } = useSession();
+  const {
+    sessions,
+    currentSessionId,
+    createSession,
+    deleteSession,
+    setCurrentSession,
+  } = useSession();
   const storeSessions = useSessionStore((s) => s.sessions);
-
-  useEffect(() => {
-    loadSessions();
-  }, [loadSessions]);
+  const storeCurrentSessionId = useSessionStore((s) => s.currentSessionId);
 
   const displaySessions = sessions.length > 0 ? sessions : storeSessions;
+  const activeSessionId = currentSessionId || storeCurrentSessionId;
 
   const handleNewChat = async () => {
     const session = await createSession();
     if (session && onClose) onClose();
   };
 
+  const handleSelectSession = (id: string) => {
+    setCurrentSession(id);
+    if (onClose) onClose();
+  };
+
+  const handleDeleteSession = (e: { stopPropagation: () => void }, id: string) => {
+    e.stopPropagation();
+    deleteSession(id);
+  };
+
+  /** 格式化时间戳为可读字符串 */
+  const formatTime = (ts: string | number): string => {
+    if (!ts) return '';
+    const date = new Date(typeof ts === 'string' ? parseInt(ts, 10) : ts);
+    if (isNaN(date.getTime())) return '';
+    const now = new Date();
+    const diffMs = now.getTime() - date.getTime();
+    const diffMin = Math.floor(diffMs / 60000);
+    if (diffMin < 1) return '刚刚';
+    if (diffMin < 60) return `${diffMin}分钟前`;
+    const diffHour = Math.floor(diffMin / 60);
+    if (diffHour < 24) return `${diffHour}小时前`;
+    const diffDay = Math.floor(diffHour / 24);
+    if (diffDay < 7) return `${diffDay}天前`;
+    return date.toLocaleDateString('zh-CN');
+  };
+
   return (
     <aside className="h-full bg-white/90 dark:bg-gray-900/90 border-r border-pink-100 dark:border-pink-900 flex flex-col">
       {/* 侧边栏头部 */}
@@ -45,14 +75,11 @@ export function Sidebar({ onClose }: SidebarProps) {
           displaySessions.map((session) => (
             <div
               key={session.id}
-              onClick={() => {
-                setCurrentSession(session.id);
-                if (onClose) onClose();
-              }}
+              onClick={() => handleSelectSession(session.id)}
               className={`
                 group flex items-center justify-between px-4 py-2.5 mx-2 rounded-lg cursor-pointer transition-colors
                 ${
-                  currentSessionId === session.id || session.id === useSessionStore.getState().currentSessionId
+                  activeSessionId === session.id
                     ? 'bg-pink-50 dark:bg-pink-900/30 text-pink-600'
                     : 'hover:bg-gray-50 dark:hover:bg-gray-800 text-gray-600 dark:text-gray-300'
                 }
@@ -63,15 +90,13 @@ export function Sidebar({ onClose }: SidebarProps) {
                 <div className="min-w-0">
                   <p className="text-sm font-medium truncate">{session.title || '新的对话'}</p>
                   <p className="text-xs text-gray-400 truncate">
-                    {session.message_count || 0} 条消息
+                    {session.message_count != null ? `${session.message_count} 条消息` : ''}
+                    {session.updated_at ? ` · ${formatTime(session.updated_at)}` : ''}
                   </p>
                 </div>
               </div>
               <button
-                onClick={(e) => {
-                  e.stopPropagation();
-                  deleteSession(session.id);
-                }}
+                onClick={(e) => handleDeleteSession(e, session.id)}
                 className="opacity-0 group-hover:opacity-100 p-1 text-gray-400 hover:text-red-400 transition-all"
                 title="删除会话"
               >