No point in calculating them for every vertex, especially when I forgot to update the calculations for the entid vertex shader.
I really don't know what I was thinking when I wrote that code. Maybe I was trying for a half angle. Now the rendered "cone" matches up with a hard-clipped cone light (soft edges stick out a bit).
Currently, only light entities get drawn to the entid buffer, and the ids are simply displayed in a window for now (not very useful yet).