Extract skips writing *palcus.itp back to source (build regenerates them
from blueprints), but the skip branch never marked the skeleton's target
path as desired, so cleanupStaleFiles deleted the committed
source/palettes/*.itp.json on every extract. Mark the skipped target as
desired so the skeletons survive.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>