Plan the switch from dollar amounts to minor units

Your payments table stores money as amount NUMERIC(12,2) in dollars, and you are adding currencies like yen that have no cents. The plan is a new amount_minor BIGINT column in each currency's smallest unit, plus a currency column. That means backfilling 120 million rows, writing both columns while both exist, then moving reads over. This table has 6 Go services writing to it, and an AI agent can write the migrations, the code and the scripts.

Which steps does the agent do, which does a person own, and where do the gates go, with what each gate proves?