List normalized receipts

Returns normalized receipts derived from the authenticated buyer's invocation history. Each receipt's settlement_status reuses the durable invocation value; for x402, ordinary free invocations retain terminal settled while granted World AgentKit trials retain free_trial, matching the immediate payment-response receipt metadata rather than changing from pending on later readback. These zero-dollar states do not claim that paid settlement occurred. Receipt items also echo openai_agents_trace when the originating execute, invoke, or x402 call supplied OpenAI Agents metadata.