[Feature Request] 模型响应时看不清第一行文字就被顶上去了影响阅读

### 🥰 需求描述

## 问题描述
模型响应时看不清第一行文字就被顶上去了太影响阅读，希望能优化模型响应的消息泡泡
## 期望
模型开始**大段文字**响应时，从出现第一行开始能让人稳定持续不被打断的阅读

### 🧐 解决方案

优化消息泡泡移动速度或者控制泡泡的高度增长方向，可以参考原版chatgpt

### 📝 补充信息

_No response_

No source file, test, or entry point is identified in the issue, so first locate the streaming response message bubble in the frontend and reproduce the behavior with a long model response. Done means the first lines remain steadily readable while a large response streams, without being pushed away abruptly.

Written by the indexing model from the issue text.