#frankly this should work for all software with layer groups. alpha clipping and masks

[airship-full-of-dragons]

for own future reference, this is how to make everything clip properly in Krita. unset all 'pass-through' layer groups, create an alpha mask from the full silhouette from the skin group, and shove it in over the lines and shadows, set the shadows and lines to clip. Now you can't color outside the lines. win!