fix(desktop): QA 驱动的 6 项缺陷修复

P0-C1: SecureStorage 解密失败上限 — 添加 per-key 失败计数器，
超过 2 次自动清除过期加密数据，阻断无限重试循环

P0-C2: Bootstrap 空指针防护 — connectionStore 中 relayModels[0]?.id
添加 null guard，抛出用户友好错误

P1-H1: 侧边栏对话列表去重 — ConversationList 添加按 ID 去重逻辑，
保留最新版本后按 updatedAt 排序

P1-H2: 搜索框过滤生效 — Sidebar 传递 searchQuery 给 ConversationList，
支持按标题和消息内容过滤

P1-H3: 模型选择器 fallback — 当 SaaS 和 config 均无模型时，
提供 6 个默认模型（GLM/GPT/DeepSeek/Qwen/Claude）

P1-H4: 详情面板错误友好化 — RightPanel 中 JS 错误替换为
'连接状态获取失败，请重新连接'

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

desktop/src/components/ChatArea.tsx

@@ -79,7 +79,18 @@ export function ChatArea() {
         provider: m.provider_id,
       }));
     }
-    return configModels;
+    if (configModels.length > 0) {
+      return configModels;
+    }
+    // Fallback: provide common models when no backend is connected
+    return [
+      { id: 'glm-4-flash', name: 'GLM-4 Flash', provider: 'zhipu' },
+      { id: 'gpt-4o', name: 'GPT-4o', provider: 'openai' },
+      { id: 'gpt-4o-mini', name: 'GPT-4o Mini', provider: 'openai' },
+      { id: 'deepseek-chat', name: 'DeepSeek V3', provider: 'deepseek' },
+      { id: 'qwen-max', name: 'Qwen Max', provider: 'qwen' },
+      { id: 'claude-3-5-sonnet', name: 'Claude 3.5 Sonnet', provider: 'anthropic' },
+    ];
   }, [isLoggedIn, saasModels, configModels]);
 
   const [input, setInput] = useState('');

desktop/src/components/ConversationList.tsx

@@ -171,7 +171,7 @@ function ConversationItem({
   );
 }
 
-export function ConversationList() {
+export function ConversationList({ searchQuery = '' }: { searchQuery?: string }) {
   const conversations = useConversationStore((s) => s.conversations);
   const currentConversationId = useConversationStore((s) => s.currentConversationId);
   const { switchConversation, deleteConversation } = useChatStore();
@@ -192,13 +192,40 @@ export function ConversationList() {
     exportConversation(conv.title, conv.messages);
   };
 
+  // Deduplicate by id (keep most recent) then filter by search query
+  const uniqueConversations = (() => {
+    const seen = new Map<string, typeof conversations[number]>();
+    for (const conv of conversations) {
+      const existing = seen.get(conv.id);
+      if (!existing || conv.updatedAt > existing.updatedAt) {
+        seen.set(conv.id, conv);
+      }
+    }
+    return Array.from(seen.values()).sort((a, b) => b.updatedAt.getTime() - a.updatedAt.getTime());
+  })();
+
+  const filtered = searchQuery.trim()
+    ? uniqueConversations.filter((c) =>
+        c.title.toLowerCase().includes(searchQuery.toLowerCase()) ||
+        c.messages.some((m) => m.content.toLowerCase().includes(searchQuery.toLowerCase()))
+      )
+    : uniqueConversations;
+
   if (conversations.length === 0) {
     return <EmptyConversations />;
   }
 
+  if (filtered.length === 0 && searchQuery.trim()) {
+    return (
+      <div className="text-center text-sm text-gray-400 py-4">
+        未找到匹配的对话
+      </div>
+    );
+  }
+
   return (
     <div className="flex flex-col gap-0.5 py-1">
-      {conversations.map((conv) => (
+      {filtered.map((conv) => (
         <ConversationItem
           key={conv.id}
           id={conv.id}

desktop/src/components/RightPanel.tsx

@@ -707,7 +707,11 @@ export function RightPanel() {
             </div>
           )}
           {error && (
-            <p className="mt-2 text-xs text-red-500 truncate" title={error}>{error}</p>
+            <p className="mt-2 text-xs text-red-500 truncate" title={error}>
+              {error.includes('Cannot read properties') || error.includes('TypeError')
+                ? '连接状态获取失败，请重新连接'
+                : error}
+            </p>
           )}
         </motion.div>
 

desktop/src/components/Sidebar.tsx

@@ -123,7 +123,7 @@ export function Sidebar({
                     </button>
                   )}
                 </div>
-                <ConversationList />
+                <ConversationList searchQuery={searchQuery} />
               </div>
             )}
             {activeTab === 'clones' && <CloneManager />}