So, a picture is in order.
Tada! I am now able to display sensible characters on the screen. And boy did I learn a lot about the ANTIC today. Phew....
What's going on here? Well, the VTIO driver is setting up the ANTIC and telling it where the character set is. Due to hardware restrictions, it must reside on a 1K boundary, so I've stuck it up in the kernel for now.
The next step is to launch a process and get its output to the screen in a sensible manner. That will take some work on the VTIO driver.