Build checklist

Before writing integration code, decide these things:

• Domain preimage.
• Ballot meaning.
• Payload meaning.
• Who proposes payloads.
• How consumers validate payloads.
• What gets stored after each accepted roll.
• What your payload producer returns for a ballot.
• What your accepted-submission hook records.
• What your observed-roll hook applies.
• Where the app stores next_ballot.
• How many Bitcoin confirmations are required.
• How missed ballots are backfilled.
• Which ZMQ notifications wake the app.
• Which polling backfill catches missed work.

If any item is unclear, keep payloads small and make the consumer idempotent.