docs: consolidate iteration 11 delivery guidance

docs/ITERATION_11.md

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+# Iteration 11 Delivery Index
+
+This iteration consolidates the operational documentation and verification
+entry points for gateway integrations, payment correctness, and payout
+reliability. The implementation is intentionally linked to the existing
+services and tests so future changes remain reviewable.
+
+## Gateway integrations
+
+- Gateway routing and fallback behavior: [`PAYMENT_ROUTING.md`](PAYMENT_ROUTING.md)
+- Provider-specific circuit breaking and degraded responses:
+  [`CIRCUIT_BREAKER.md`](CIRCUIT_BREAKER.md)
+- Webhook authentication and replay protection:
+  [`../WEBHOOK_VERIFICATION.md`](../WEBHOOK_VERIFICATION.md)
+
+When adding a provider, cover quote creation, timeout behavior, provider
+failure mapping, and idempotent retry behavior in the provider test suite.
+
+## Payment correctness
+
+- Payment reconciliation and mismatch handling:
+  [`PAYMENT_RECONCILIATION.md`](PAYMENT_RECONCILIATION.md)
+- Split allocation invariants:
+  [`SPLIT_PAYMENTS.md`](SPLIT_PAYMENTS.md)
+- Refund and settlement behavior:
+  [`REFUND_ENGINE.md`](REFUND_ENGINE.md)
+
+The minimum correctness checks are conservation of value, a single terminal
+state transition, idempotent replay of the same request, and preservation of
+the original payment identifier in emitted events.
+
+## Payout reliability
+
+- Retry, backoff, and dead-letter behavior:
+  [`PAYOUT_RELIABILITY.md`](PAYOUT_RELIABILITY.md)
+- Approval gates and operator recovery:
+  [`PAYOUT_APPROVALS.md`](PAYOUT_APPROVALS.md)
+- Background job operation:
+  [`JOB_QUEUE.md`](JOB_QUEUE.md)
+
+Reliability changes must include a failure injection test, a bounded retry
+policy, and an operator-visible terminal state. Do not retry a request unless
+the provider operation is idempotent or its outcome can be reconciled safely.
+
+## Verification
+
+Run the repository checks from the root before merging:
+
+```bash
+npm test
+npm run lint
+npm run typecheck
+```
+
+Backend-only changes should also run the targeted backend test project. Update
+the linked document when an endpoint, provider contract, or recovery state
+changes.