🐛 alternate screen buffer doesn't work using NuShell

I've noticed that in NuShell when I scroll using my mouse that Delta wasn't scrolling, but rather the entire terminal itself.
Going back to Zsh, I found out that the scroll works again. The difference is that in Zsh the alternate screen buffer was enabled, while in NuShell it wasn't.

This isn't a problem in other applications. `man` and Bat work fine, just Delta has this issue (as far as I know).

The issue names no files or tests. First reproduce mouse scrolling in Delta under NuShell, then compare the terminal behavior with Zsh and with `man` or Bat; investigate where Delta enters or relies on the alternate screen buffer. Done means scrolling in NuShell moves through Delta's output rather than the whole terminal, without regressing the working shells.

Written by the indexing model from the issue text.