Proper clear on macOS

[nixpulvis]

As discovered in alacritty/alacritty#2329 circa 2019, if you're running on macOS you still need to install a newer version of ncurses (e.g. brew install ncurses) and add it to your path (e.g. PATH=/opt/homebrew/opt/ncurses/bin:$PATH) for clear to properly clear the whole terminal buffer.

I ran into this because I haven't set my default shell in Zed to fish yet and forgot to append the updated clear command to my sh/bash init files.

Hope this helps someone else who is frustrated by this.