SimulatedPayment

Stands in for a real SDK round-trip when a gateway has no live sandbox credentials (GatewayStatus.MOCK_MODE). A short suspend delay mimics the SDK hop; the outcome is scripted (not random) so the Lab timeline is deterministic and every mock-mode gateway can be demoed end-to-end with zero credentials.

Lives in core:payments-api rather than core:common (its natural home per the plan) because it builds PaymentResult/RedactedPayload values, and core:common cannot depend back on core:payments-api without a module cycle — payments-api already depends on common.