I still don't understand the entire state space here, so I'm trying to
err on the side of improving discoverability of the `ctrl-h` escape
hatch. Without requiring too wide a window to show all hotkeys on the
menu.
I wish I could just hide KEY_BACKSPACE and prevent myself from using it
by accident.
Then again, I'm not making this smarts available in Teliva programs
themselves. Just for the Teliva environment.