Scrollback for non-raw terminals

[willothy]

Can check if terminal is raw via the termios crate. All terminals can have scrollback buffers since dynamically checking if a terminal needs one would be complicated, but scroll events should be sent directly to terminals in raw mode instead of affecting the screen's view.

TODO:

• Necessary changes:
  • Restructure process output handling to allow buffering before passthrough over RPC to client.
  • Refactor input handling to allow for more complex keymaps (refactor!: rework input handling #7)
    • Migrate fully from Termion to Termwiz?
• Scrollback implementation
  • Add per-session scrollback buffer with bounded capacity (~1000 lines?)
  • Create basic "view" model to control the view over the scrollback buffer