Registers a script stake credential so a later withdrawal from it does not fail on ledger for the wrong reason.

#157 removed-consumer-encoding: the consumer-registration builder is DELETED with the pinned consumer it registered. There is no consumer script to register and no mandatory withdrawal left to make possible, and a function that registers nothing would be a trap for the next reader. What remains is the generic credential registration the exhibit controls use directly; it authorizes nothing by itself.