bug: `clear` command does not clear scrollback buffer by default

<img width="640" height="480" alt="Image" src="https://github.com/user-attachments/assets/1158a949-4396-4e8b-91fb-29c602d294ca" />


According to the manpage at https://invisible-island.net/ncurses/man/clear.1.html, the `clear` command clears the scroll back buffer by default, but preserves it when the `-x` option is passed. 
