功能需求说明

没有清除终端信息的选项，比如说我用串口连接了一个设备，开机会有很多log，当我想再次开机看log时，我不希望上次的log影响到我，所以需要这个选项，再则，有的人在终端不希望有时间戳以及行号，尤其是屏幕小的用户

Start by locating the terminal display and settings entry points for the Serial terminal, then review how startup output is retained and rendered. Done means users can clear existing terminal content and independently hide timestamps and line numbers, with the options working for narrow screens without affecting new terminal output.

Written by the indexing model from the issue text.