Summary

• Clarify that payment-identifier idempotency records should bind an id to a normalized request fingerprint.
• Document same-id/different-fingerprint handling as a conflict case for resource servers and facilitators.
• Add production guidance to the Go server and facilitator payment-identifier examples.

Duplicate check

• Checked open x402 idempotency PRs before starting. Existing open PRs cover retry/idempotency utility work (feat: Add retry and idempotency utility package #1104), facilitator settle idempotency (feat(go): add transaction idempotency for facilitator settle #790), and a client example retry fix (fix retry in payment-identifier client example  #1332).
• This PR is intentionally docs-only and scoped to request binding guidance for the existing payment-identifier extension.

Verification

• git diff --check

No package-level formatter was run because this is a markdown-only change and this fresh clone has no local node_modules installed.