Registered before the human's figures: a reported slip stays as locked¶

The check page locks the human's label and outside-names answer before it reveals rater A's. A checker can notice a mis-click only after the reveal, and a correction made after seeing the rater is no longer blind, so it does not replace the locked answer. The rule, fixed before any human agreement is computed: every human figure is read on the answers as locked, and each pair a reported slip touches is also reported without that item (human_slips and the without slips pairs). Slips are marked on the page beside the locked answer and saved with the check; label_audit_agreement.py reads them from there, and --slip ITEM:FIELD adds one by hand.