feat(chat): improve resilience and collapsible sidebar

问题描述:\n- 刷新页面、切后台或手机锁屏后，进行中的对话容易丢失，SSE 断开时前端还会插入假的错误气泡\n- 移动端首屏会话列表会短暂遮住聊天区\n- 桌面端侧栏无法折叠，在窄窗口和缩放场景占用过多横向空间\n\n复现路径:\n- 发起一轮对话，在模型仍在输出时刷新页面或锁屏后再回到页面\n- 在窄屏设备首次打开聊天页，观察会话列表首帧覆盖聊天内容\n- 在桌面端缩窄浏览器窗口，观察侧栏始终保持完整宽度\n\n修复思路:\n- 为 chat store 增加本地缓存、水合、in-flight 标记和轮询恢复，SSE 断开后静默从服务端回补真实结果\n- 将运行中指示统一到 isRunActive，让实时流式与恢复轮询共享同一状态\n- 在 ChatPanel 首帧同步读取媒体查询，避免移动端会话列表闪烁覆盖\n- 为侧栏增加可持久化的桌面折叠状态，并补充对应文案与回归测试

packages/client/src/components/hermes/chat/ChatPanel.vue

@@ -11,7 +11,15 @@ const chatStore = useChatStore()
 const message = useMessage()
 const { t } = useI18n()
 
-const showSessions = ref(true)
+// Initialize synchronously from the media query so first paint is correct.
+// On narrow viewports the session list is an absolute-positioned overlay
+// (z-index 10) on top of the chat area; if we default to `true`, onMounted
+// only flips it to `false` AFTER the first render, causing a visible flash
+// where the session list covers the chat content ("auto-fixes after a
+// moment" — that was the race).
+const showSessions = ref(
+  typeof window === 'undefined' || !window.matchMedia('(max-width: 768px)').matches,
+)
 let mobileQuery: MediaQueryList | null = null
 
 function handleSessionClick(sessionId: string) {

packages/client/src/components/hermes/chat/MessageList.vue

@@ -45,7 +45,7 @@ watch(
   scrollToBottom,
 );
 watch(
-  () => chatStore.isStreaming,
+  () => chatStore.isRunActive,
   (v) => {
     if (v) scrollToBottom();
   },
@@ -61,7 +61,7 @@ watch(currentToolCalls, scrollToBottom);
     </div>
     <MessageItem v-for="msg in displayMessages" :key="msg.id" :message="msg" />
     <Transition name="fade">
-      <div v-if="chatStore.isStreaming" class="streaming-indicator">
+      <div v-if="chatStore.isRunActive" class="streaming-indicator">
         <video
           :src="isDark ? thinkingVideoDark : thinkingVideoLight"
           autoplay