Billing and usage fields

The usage structure is broadly consistent across models. The key fields to keep are usage and billing_status.

Field	Description
`completion_tokens`	Output token count
`total_tokens`	Total token count
`billing_status`	Billing state such as `frozen`, `settling`, `settled`, or `refunded`

Billing notes

Save id, model, and usage for every task.
Use the query response and console billing data for reconciliation.
Fast model limits such as resolution and duration are determined by /v1/models.
Refund handling after failure, cancel, or timeout should follow billing_status.