How it works. The leaf lives at neighborhoods/<building>/membership.json. When a neighbor joins, their phone mints the seat and offers a receipt (with the ticket's number) to the union's mailbox. You fold that number in here: one line into the settled list. The join gate reads the leaf online, before any later join settles — a number already on the leaf cannot be taken again. This desk only drafts; you save, commit, and deploy, and the fold lands when the file ships — exactly like a paper book writing in a name. To publish a mailbox for receipts, set warden_email in membership.json and the join page will offer it. The leaf carries ticket numbers, never people.