get_available_change_sns — Group 9, Code 91
Reserve or discover serial numbers needed for change operations.
Purpose
get_available_change_sns returns or reserves serial numbers needed for follow-up break or join flows. Treat it as the inventory/discovery step for controlled denomination changes.
Legacy wire reference — verify before relying
This byte layout was restored from the pre-V2 documentation (commit ceba44b). It has not been cross-checked against the current raidax implementation in every detail.