fix(phase2e-2): 视频 HD 分辨率 + toolbar 防溢出 + 聊天按钮 toggle

问题
1. 进入会议后视频比预览页更"近、更糊"
   · 预览 / startLocalVideo 均固定 640x480，mediasoup 视频轨清晰度偏低
   · 进房后 videoTile cover 裁切在大画布更明显 → 观感"放大"
2. 会议内聊天 / 邀请 / 成员按钮"点击无反应"
   · 核心：.body flex 子内容过高时 toolbar 未固定收缩，被挤出视口
     下方 (y > vh)，用户点击位置在屏幕外
   · 次要：openChat 仅 set true，已打开状态下再次点击无视觉反馈
3. 聊天按钮无法关闭面板：只有面板内 × 按钮能关

修复
- store/meeting.js startLocalVideo + preview.vue getUserMedia 统一
  改为 ideal 1280x720 + frameRate ideal 24 / max 30，浏览器在设备不
  支持时自动降级；进房与预览视觉表现一致
- components/meeting/MeetingToolbar.vue .toolbar 加 flex-shrink:0
  + position:relative + z-index:15，保证 toolbar 永远贴底不被 body
  压缩，且点击层级高于 ChatPanel 背景
- pages/meeting/room.vue .top-bar 加 flex-shrink:0，避免 body 溢出
  时顶栏压缩引发整体错位
- pages/meeting/room.vue openChat 改 toggle：已打开则关闭，未打开则
  展开并 markChatsRead，交互更符合直觉

验证（Playwright 1024x576）
- 预览 getVideoTracks()[0].getSettings() → 1280x720 / 24fps ✓
- 进房后 localVideo settings 同样 1280x720 ✓
- 聊天按钮 boundingRect y=505 bottom=567 ≤ vh 576，inViewport=true ✓
- 点击聊天 → chat-col.open=true 宽度 320.5px；再点击 → open=false ✓
- 截图 room-hd-chat-open.png：视频清晰、聊天面板展开、toolbar 贴底

Made-with: Cursor

frontend/src/components/meeting/MeetingToolbar.vue

@@ -123,6 +123,11 @@ const emitIf = (name) => {
   background: rgba(17, 24, 39, 0.88);
   backdrop-filter: blur(16px);
   border-top: 1rpx solid rgba(255, 255, 255, 0.08);
+  /* flex-shrink:0 保证 body 内容高度过大时不会把 toolbar 挤出视口；
+     position:relative + z-index 提升按钮点击层级，避免 ChatPanel 遮挡 */
+  flex-shrink: 0;
+  position: relative;
+  z-index: 15;
 }
 
 .btn {

frontend/src/pages/meeting/preview.vue

@@ -197,8 +197,8 @@ const startPreview = async () => {
     const constraints = {
       audio: selectedAudioId.value ? { deviceId: { exact: selectedAudioId.value } } : true,
       video: selectedVideoId.value
-        ? { deviceId: { exact: selectedVideoId.value }, width: 640, height: 480 }
-        : { width: 640, height: 480 }
+        ? { deviceId: { exact: selectedVideoId.value }, width: { ideal: 1280 }, height: { ideal: 720 }, frameRate: { ideal: 24, max: 30 } }
+        : { width: { ideal: 1280 }, height: { ideal: 720 }, frameRate: { ideal: 24, max: 30 } }
     }
     previewStream = await navigator.mediaDevices.getUserMedia(constraints)
     hasPermission.value = true

frontend/src/pages/meeting/room.vue

@@ -379,6 +379,11 @@ const onCamToggle = async () => {
 const openInvite = () => { inviteVisible.value = true }
 const openMembers = () => { memberVisible.value = true }
 const openChat = () => {
+  // 点击工具栏聊天按钮时进行切换：已打开 → 关闭；未打开 → 打开并标记已读
+  if (chatVisible.value) {
+    chatVisible.value = false
+    return
+  }
   chatVisible.value = true
   meetingStore.markChatsRead()
 }
@@ -555,6 +560,7 @@ onUnload(() => {
   background: linear-gradient(to bottom, rgba(0, 0, 0, 0.55), rgba(0, 0, 0, 0));
   position: relative;
   z-index: 5;
+  flex-shrink: 0;
 }
 
 .top-left {

frontend/src/store/meeting.js

@@ -648,9 +648,11 @@ export const useMeetingStore = defineStore('meeting', () => {
   const startLocalVideo = async (deviceId) => {
     if (!_engine) throw new Error('未连接')
     if (localProducers.video) return
+    // 与预览页保持一致的 HD 分辨率（ideal 1280x720，允许浏览器在设备不支持时降级）
     const videoConstraints = {
-      width: 640,
-      height: 480,
+      width: { ideal: 1280 },
+      height: { ideal: 720 },
+      frameRate: { ideal: 24, max: 30 },
       ...(deviceId ? { deviceId: { exact: deviceId } } : {})
     }
     const stream = await navigator.mediaDevices.getUserMedia({ video: videoConstraints })