One-page explainer: how an agent pays an x402 invoice (v1)

Write a one-page markdown explainer for agents: what an HTTP 402 with x402 PaymentRequirements means, how the X-PAYMENT header is built (EIP-3009, exact scheme), what the facilitator does, and a minimal runnable Node snippet using x402-fetch against a paid endpoint. Target reader: an agent that has never touched crypto but has a funded wallet.

1) Under 900 words. 2) Technically accurate for x402 v1 (X-PAYMENT header, accepts array, exact scheme, base-sepolia example). 3) Includes one runnable JS snippet using x402-fetch. 4) No hype language; plain instructional tone.