refactor: 设置面板改为右侧抽屉，修复布局跳动问题

- ConfigPanel 重写为 Drawer：右侧 320px 滑入面板 + 半透明遮罩
- 设置按钮始终可见，不依赖连接状态
- 抽屉不推挤主布局，点击遮罩或✕关闭
- 设置项分组显示，带功能描述文案

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

frontend/src/App.css

@@ -140,7 +140,7 @@ body {
 /* ---- 左侧视频面板 ---- */
 
 .video-panel {
-  width: 340px;
+  width: 400px;
   flex-shrink: 0;
   display: flex;
   flex-direction: column;
@@ -392,44 +392,107 @@ body {
   border: 1px solid rgba(245, 158, 11, 0.2);
 }
 
-/* ---- Config Panel ---- */
+/* ---- Drawer (Config Panel) ---- */
 
-.config-panel {
+.drawer-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 100;
+  background: rgba(0, 0, 0, 0.4);
+  backdrop-filter: blur(2px);
+  animation: fadeIn 0.2s ease;
+}
+
+.drawer {
+  position: absolute;
+  top: 0;
+  right: 0;
+  bottom: 0;
+  width: 320px;
   background: var(--color-surface);
-  border-bottom: 1px solid var(--color-border);
-  padding: 16px 24px;
+  border-left: 1px solid var(--color-border);
+  display: flex;
+  flex-direction: column;
+  animation: slideInRight 0.25s ease;
+  box-shadow: -8px 0 24px rgba(0, 0, 0, 0.3);
+}
+
+.drawer__header {
   display: flex;
   align-items: center;
-  gap: 24px;
+  justify-content: space-between;
+  padding: 14px 16px;
+  border-bottom: 1px solid var(--color-border);
   flex-shrink: 0;
 }
 
-.config-panel__header {
-  display: flex;
-  align-items: center;
-  gap: 8px;
+.drawer__title {
   font-weight: 600;
-  font-size: 0.85rem;
+  font-size: 0.9rem;
 }
 
-.config-panel__close {
+.drawer__close {
   background: none;
   border: none;
   color: var(--color-text-muted);
   cursor: pointer;
-  font-size: 0.9rem;
-  padding: 2px 6px;
+  font-size: 1rem;
+  padding: 4px 8px;
+  border-radius: var(--radius-sm);
+  transition: all 0.15s;
 }
 
-.config-panel__close:hover {
+.drawer__close:hover {
+  background: var(--color-surface-2);
   color: var(--color-text);
 }
 
+.drawer__body {
+  flex: 1;
+  overflow-y: auto;
+  padding: 16px;
+}
+
+/* ---- Config Group ---- */
+
+.config-group {
+  margin-bottom: 20px;
+}
+
+.config-group__title {
+  font-size: 0.7rem;
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.8px;
+  color: var(--color-text-muted);
+  margin-bottom: 12px;
+  padding-bottom: 8px;
+  border-bottom: 1px solid var(--color-border);
+}
+
 .config-row {
   display: flex;
   align-items: center;
-  gap: 8px;
+  justify-content: space-between;
+  padding: 10px 0;
   font-size: 0.82rem;
+  color: var(--color-text);
+  cursor: pointer;
+}
+
+.config-row__info {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.config-row__label {
+  font-weight: 500;
+  color: var(--color-text);
+}
+
+.config-row__desc {
+  font-size: 0.72rem;
   color: var(--color-text-muted);
 }
 
@@ -439,8 +502,15 @@ body {
   color: var(--color-text);
   border: 1px solid var(--color-border);
   border-radius: var(--radius-sm);
-  padding: 4px 8px;
+  padding: 5px 10px;
   font-size: 0.8rem;
+  cursor: pointer;
+}
+
+.config-row input[type="checkbox"] {
+  width: 18px;
+  height: 18px;
+  cursor: pointer;
 }
 
 /* ---- Toast ---- */
@@ -559,6 +629,16 @@ body {
   to { opacity: 1; transform: translateX(0); }
 }
 
+@keyframes fadeIn {
+  from { opacity: 0; }
+  to { opacity: 1; }
+}
+
+@keyframes slideInRight {
+  from { transform: translateX(100%); }
+  to { transform: translateX(0); }
+}
+
 /* ---- Scrollbar ---- */
 
 ::-webkit-scrollbar {

frontend/src/App.tsx

@@ -54,15 +54,13 @@ function App() {
           <span className={`badge badge--${connectionStatus}`}>
             {isConnected ? "已连接" : connectionStatus === "connecting" ? "连接中..." : "未连接"}
           </span>
-          {isConnected && (
-            <button
-              className="btn-icon"
-              onClick={() => setShowConfig((v) => !v)}
-              title="设置"
-            >
-              ⚙️
-            </button>
-          )}
+          <button
+            className="btn-icon"
+            onClick={() => setShowConfig((v) => !v)}
+            title="设置"
+          >
+            ⚙️
+          </button>
         </div>
       </header>
 

frontend/src/components/ConfigPanel/index.tsx

@@ -1,5 +1,5 @@
 // ============================================================
-// ConfigPanel — 会话配置面板
+// ConfigPanel — 右侧抽屉式配置面板
 // 职责：TTS 开关、detail level 切换、语言选择
 // ============================================================
 
@@ -13,43 +13,60 @@ interface ConfigPanelProps {
 
 export function ConfigPanel({ config, onUpdate, onClose }: ConfigPanelProps) {
   return (
-    <div className="config-panel">
-      <div className="config-panel__header">
-        <span>设置</span>
-        <button className="config-panel__close" onClick={onClose}>✕</button>
+    <div className="drawer-overlay" onClick={onClose}>
+      <div className="drawer" onClick={(e) => e.stopPropagation()}>
+        <div className="drawer__header">
+          <span className="drawer__title">设置</span>
+          <button className="drawer__close" onClick={onClose}>✕</button>
+        </div>
+
+        <div className="drawer__body">
+          <div className="config-group">
+            <div className="config-group__title">会话</div>
+
+            <label className="config-row">
+              <div className="config-row__info">
+                <span className="config-row__label">语音回答</span>
+                <span className="config-row__desc">AI 回答时同步播放语音</span>
+              </div>
+              <input
+                type="checkbox"
+                checked={config.ttsEnabled}
+                onChange={(e) => onUpdate({ ttsEnabled: e.target.checked })}
+              />
+            </label>
+
+            <label className="config-row">
+              <div className="config-row__info">
+                <span className="config-row__label">图像精度</span>
+                <span className="config-row__desc">高精度适合识别文字，低精度省流量</span>
+              </div>
+              <select
+                value={config.detailLevel}
+                onChange={(e) => onUpdate({ detailLevel: e.target.value as "low" | "high" })}
+              >
+                <option value="low">低</option>
+                <option value="high">高</option>
+              </select>
+            </label>
+
+            <label className="config-row">
+              <div className="config-row__info">
+                <span className="config-row__label">语言</span>
+                <span className="config-row__desc">交互语言偏好</span>
+              </div>
+              <select
+                value={config.language}
+                onChange={(e) => onUpdate({ language: e.target.value })}
+              >
+                <option value="zh-CN">中文</option>
+                <option value="en-US">English</option>
+                <option value="ja-JP">日本語</option>
+              </select>
+            </label>
+          </div>
+        </div>
       </div>
-
-      <label className="config-row">
-        <span>语音回答</span>
-        <input
-          type="checkbox"
-          checked={config.ttsEnabled}
-          onChange={(e) => onUpdate({ ttsEnabled: e.target.checked })}
-        />
-      </label>
-
-      <label className="config-row">
-        <span>图像精度</span>
-        <select
-          value={config.detailLevel}
-          onChange={(e) => onUpdate({ detailLevel: e.target.value as "low" | "high" })}
-        >
-          <option value="low">低（省流量）</option>
-          <option value="high">高（细节丰富）</option>
-        </select>
-      </label>
-
-      <label className="config-row">
-        <span>语言</span>
-        <select
-          value={config.language}
-          onChange={(e) => onUpdate({ language: e.target.value })}
-        >
-          <option value="zh-CN">中文</option>
-          <option value="en-US">English</option>
-          <option value="ja-JP">日本語</option>
-        </select>
-      </label>
     </div>
   );
 }