Draft personas with a model

Returns DRAFTS and persists nothing. That separation is deliberate: generation is the step most likely to produce something nobody wanted, and a route that both invented and saved would make "let me see what you'd suggest" indistinguishable from "fill my project with these".

It is also why there is no idempotency key — a call with no effect has nothing to de-duplicate, and offering one would imply the drafts are stable across retries when they are not.

SPENDS. This runs models on your organization's account and is metered two ways: a per-minute burst brake (429, retry in seconds) and your plan's daily budget (429, resets at UTC midnight). Both normally carry Retry-After — honor it when it is there, and back off on your own when it is not.