Why we forbid floating-point amounts
CHINAUSDT stores amounts as integer minor units, writes ledger before balance, and settles once per order.
Every cent must reconcile. Floating point introduces unexplainable dust, so CHINAUSDT forbids float amounts end-to-end.
Pass amount as an integer minor unit. Format for display only after the wire. Settlement writes the ledger first, then balance, in one transaction, idempotent by order id.