feat(web): 在窄屏幕宽度下自动折叠并浮动对话侧边栏

为 .chat-main 添加了 ResizeObserver，当消息区域宽度低于 600px 时自动折叠对话历史侧边栏，避免界面挤压。同时添加了浮动状态，使侧边栏在小屏幕上重新打开时以覆盖层形式显示。

web/src/components/AgentChatComponent.vue

@@ -4,6 +4,7 @@
       :current-chat-id="currentChatId"
       :chats-list="chatsList"
       :is-sidebar-open="chatUIStore.isSidebarOpen"
+      :is-floating="isSidebarFloating"
       :is-initial-render="localUIState.isInitialRender"
       :single-mode="props.singleMode"
       :agents="agents"
@@ -72,7 +73,7 @@
 
       <div class="chat-content-container">
         <!-- Main Chat Area -->
-        <div class="chat-main">
+        <div class="chat-main" ref="chatMainRef">
           <div class="chat-box">
             <div class="conv-box" v-for="(conv, index) in conversations" :key="index">
               <AgentMessageComponent
@@ -491,6 +492,9 @@ const isProcessing = computed(() => isStreaming.value)
 
 // ==================== SCROLL & RESIZE HANDLING ====================
 const scrollController = new ScrollController('.chat-main')
+const chatMainRef = ref(null)
+const isSidebarFloating = ref(false)
+let chatMainResizeObserver = null
 
 onMounted(() => {
   nextTick(() => {
@@ -498,6 +502,30 @@ onMounted(() => {
     if (chatMainContainer) {
       chatMainContainer.addEventListener('scroll', scrollController.handleScroll, { passive: true })
     }
+
+    if (window.ResizeObserver && chatMainRef.value) {
+      chatMainResizeObserver = new ResizeObserver((entries) => {
+        for (const entry of entries) {
+          const width = entry.contentRect.width
+          const isTakingSpace = chatUIStore.isSidebarOpen && !isSidebarFloating.value
+          
+          if (isTakingSpace) {
+            if (width < 600) {
+              isSidebarFloating.value = true
+              chatUIStore.isSidebarOpen = false
+              localStorage.setItem('chat_sidebar_open', 'false')
+            }
+          } else {
+            if (width >= 880) {
+              isSidebarFloating.value = false
+            } else {
+              isSidebarFloating.value = true
+            }
+          }
+        }
+      })
+      chatMainResizeObserver.observe(chatMainRef.value)
+    }
   })
   setTimeout(() => {
     localUIState.isInitialRender = false
@@ -506,6 +534,9 @@ onMounted(() => {
 
 onUnmounted(() => {
   scrollController.cleanup()
+  if (chatMainResizeObserver) {
+    chatMainResizeObserver.disconnect()
+  }
   // 清理所有线程状态
   resetOnGoingConv()
 })

web/src/components/ChatSidebarComponent.vue

@@ -1,7 +1,7 @@
 <template>
   <div
     class="chat-sidebar"
-    :class="{ 'sidebar-open': chatUIStore.isSidebarOpen, 'no-transition': isInitialRender }"
+    :class="{ 'sidebar-open': chatUIStore.isSidebarOpen, 'no-transition': isInitialRender, 'is-floating': isFloating }"
   >
     <div class="sidebar-content">
       <div class="sidebar-header">
@@ -146,6 +146,10 @@ const props = defineProps({
     type: Boolean,
     default: false
   },
+  isFloating: {
+    type: Boolean,
+    default: false
+  },
   singleMode: {
     type: Boolean,
     default: true
@@ -295,6 +299,20 @@ const togglePin = (chatId) => {
     transition: none !important;
   }
 
+  &.is-floating {
+    position: absolute;
+    z-index: 100;
+    left: 0;
+    top: 0;
+    bottom: 0;
+    height: 100%;
+    
+    &.sidebar-open {
+      box-shadow: 4px 0 16px rgba(0, 0, 0, 0.08);
+      border-right: none;
+    }
+  }
+
   &.sidebar-open {
     width: 280px;
     max-width: 300px;