Backlog: Provide buffer scrolling when on main screen (not alternate)

[imdaveho]

Problem to Solve
Currently, we ignore carriage returns and prevent the buffer from scrolling down. This is in line with the idea that the screen is "a canvas". The assumption at the time is that "scrolling" can be implementing "virtually"--which is just a repaint of the existing screen with the next line.

However! While this works for the alternate screen, it is a different story on the main screen. In the main screen's case, we want to maintain typical console/terminal behaviour.

Tasks

• test to see if this is actually an issue for main screen (both raw and cook modes)
• provide support to maintain regular terminal behavior in the main screen