fix(desktop): 替换 require() 为 ES import — 修复生产构建崩溃

- connectionStore: 2 处 require() → loadConversationStore() 异步预加载 + 闭包引用
- saasStore: 1 处 require() → await import()（logout 是 async）
- llm-service: 1 处 require() → 顶层 import（无循环依赖）
- streamStore: 移除重复动态导入，统一使用顶层 useConnectionStore
- tsc --noEmit 0 errors

desktop/src/store/connectionStore.ts

@@ -30,6 +30,16 @@ import { useConfigStore } from './configStore';
 import { createLogger } from '../lib/logger';
 import { secureStorage } from '../lib/secure-storage';
 
+// 延迟加载 conversationStore 避免循环依赖
+// connect() 是 async 函数，在其中 await import() 是安全的
+let _conversationStore: typeof import('./chat/conversationStore') | null = null;
+async function loadConversationStore() {
+  if (!_conversationStore) {
+    try { _conversationStore = await import('./chat/conversationStore'); } catch { /* not loaded yet */ }
+  }
+  return _conversationStore;
+}
+
 const log = createLogger('ConnectionStore');
 
 // === Mode Selection ===
@@ -492,8 +502,8 @@ export const useConnectionStore = create<ConnectionStore>((set, get) => {
               // 优先使用 conversationStore 的 currentModel，如果设置了的话
               let preferredModel: string | undefined;
               try {
-                const { useConversationStore } = require('./chat/conversationStore');
-                preferredModel = useConversationStore.getState().currentModel;
+                const cs = await loadConversationStore();
+                preferredModel = cs?.useConversationStore.getState().currentModel;
               } catch {
                 // conversationStore 可能尚未初始化
               }
@@ -553,13 +563,9 @@ export const useConnectionStore = create<ConnectionStore>((set, get) => {
               );
               const relayClient = createSaaSRelayGatewayClient(session.saasUrl, () => {
                 // 每次调用时读取 conversationStore 的 currentModel，fallback 到第一个可用模型
-                try {
-                  const { useConversationStore } = require('./chat/conversationStore');
-                  const current = useConversationStore.getState().currentModel;
-                  return (current && validBrowserModelIds.has(current)) ? current : fallbackModelId;
-                } catch {
-                  return fallbackModelId;
-                }
+                // 注意：这里不能用 await（同步回调），但 conversationStore 已在上方 loadConversationStore() 中加载
+                const current = _conversationStore?.useConversationStore.getState().currentModel;
+                return (current && validBrowserModelIds.has(current)) ? current : fallbackModelId;
               });
 
               set({