Add x402 Preflight MCP server - #25

Thanks for the detailed submission. The registry validation passes, and the live endpoint responds correctly to initialize and tools/list.

However, the proposed install command uses mcp-remote, while two of the three tools require an x402-capable client. An unpaid audit call returns HTTP 402 with the payment requirements in the PAYMENT-REQUIRED header. mcp-remote does not appear to handle the required approval, signing, and retry flow, so this configuration currently guarantees access only to the free inspection tool.

Please either:

1. provide and test an x402-aware stdio bridge and update the install configuration; or
2. clearly state that mcp-remote supports only the free tool and that paid calls require a direct x402-compatible client.

Please also validate all three tools through the exact published install command, not only through direct HTTP requests.

Updated the published install in 43c8d51 to the canonical remote:

npx -y mcp-remote https://x402.chikocorp.com/mcp

Revalidated with mcp-remote 0.8.3:

• MCP initialize: passed.
• tools/list: passed and returned all three declared tools.
• inspect_x402_endpoint: executed successfully and returned an ALLOW result for the live 0.05 USDC Base challenge.
• audit_x402_endpoint: surfaced the expected HTTP 402 as JSON-RPC error -32001; no payment was sent.
• python validate.py: passed all 209 registry files.

The registry description still states explicitly that the published bridge supports discovery and the free inspection tool only; paid calls require a direct x402-compatible client able to approve, sign, and retry payment.