fix preview dialog and waveform behavior

frontend/src/components/assistant-editor/debug-preview.tsx

@@ -1050,9 +1050,8 @@ function DebugVoicePanel({
         </div>
       </div>
 
-      {/* 底部双轨波形:会话连通后默认展开,空闲时收起 */}
+      {/* 底部双轨波形默认收起；展开状态只由用户操作控制。 */}
       <WaveformTimelinePanel
-        key={status === "connected" ? "active" : "idle"}
         defaultOpen={false}
         userStream={localStream}
         agentStream={remoteStream}

frontend/src/components/client-message-dialog.tsx

@@ -215,6 +215,9 @@ export function ClientMessageDialog({
         className="gap-5 sm:max-w-md"
         portalContainer={container}
         contained={contained}
+        overlayClassName={
+          contained ? "bg-black/20 backdrop-blur-md" : undefined
+        }
         showCloseButton={message?.dismissible ?? true}
         onEscapeKeyDown={(event) => {
           if (!message?.dismissible) event.preventDefault();

frontend/src/components/ui/dialog.tsx

@@ -57,15 +57,17 @@ function DialogContent({
   showCloseButton = true,
   portalContainer,
   contained = false,
+  overlayClassName,
   ...props
 }: React.ComponentProps<typeof DialogPrimitive.Content> & {
   showCloseButton?: boolean
   portalContainer?: Element | DocumentFragment | null
   contained?: boolean
+  overlayClassName?: string
 }) {
   return (
     <DialogPortal container={portalContainer}>
-      <DialogOverlay contained={contained} />
+      <DialogOverlay contained={contained} className={overlayClassName} />
       <DialogPrimitive.Content
         data-slot="dialog-content"
         className={cn(