This PR adds an end-to-end example demonstrating how a client can verify a server's identity using ACK ID before purchasing access to a protected route with x402.

The example includes:

• A Hono server that issues a signed ControllerCredential from an /identify endpoint and protects a /buy route with x402-hono.
• A client script that verifies the credential and then uses x402-fetch to complete the purchase.
• A pnpm run setup command to simplify local key generation.

To Test:

1. cd examples/x402
2. pnpm install
3. pnpm run setup
4. Create a .env file with a wallet PRIVATE_KEY for the buyer wallet.
5. Run pnpm run dev and pnpm run buy in separate terminals.