Errors

• model_not_available — the registry row is not available. No provider was called.
• provider_not_configured — no inference adapter is configured.
• paid_generation_disabled — public generation is still gated off.
• pricing_not_configured — there is no positive published price.
• insufficient_credits — the prepaid balance cannot cover the reserve.
• idempotency_conflict — the key was reused with a different request.
• missing_idempotency_key — POST /v1/jobs requires the header.