fix(pstack): drop "Must always apply." from unslop description
Merged
PO
6d ago+1+1+0123456789-1-1-0123456789
The unslop skill sets disable-model-invocation: true, so it never runs on its own. The description still says "Must always apply.", which contradicts that, and agents read it as a command. This change deletes that sentence.
This carries @jhneves's change from #234, rebased onto current main. The commit credits them with a Co-authored-by: trailer.

