feat: add x402 and mpp example

[brendanjryan]

Summary

• Add an example Hono server with mpp-only, x402-only, and composed paid routes
• Add a TypeScript example client that exercises mpp and x402 flows against live facilitators
• Default x402 settlement to the free x402.rs Base Sepolia test facilitator
• Parse x402 offers alongside Payment-auth challenges on mixed 402 responses
• Add per-payment x402 nonce binding so repeated live facilitator payments work

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/mppx@500

commit: 78ed00f