Add agent trust verification before x402 payments

Currently mcp-x402 creates x402 payment headers — great for enabling agent payments.

But how does the paying agent know the **receiving agent is trustworthy**?

**agentfolio-mcp** solves this: 8 MCP tools for checking agent trust scores, verification levels, and on-chain attestations before sending payment.

## Example workflow
1. Agent discovers a service via x402
2. Before paying, agent calls `check_trust` to verify the service provider
3. Trust score > threshold → proceed with payment
4. Trust score too low → skip or flag

## Quick start
```bash
npx agentfolio-mcp
```

200+ agents registered, 14 verification types, on-chain attestations on Solana mainnet.

- **npm:** [agentfolio-mcp](https://www.npmjs.com/package/agentfolio-mcp)
- **GitHub:** [0xbrainkid/satp-mcp](https://github.com/0xbrainkid/satp-mcp)
- **Platform:** [agentfolio.bot](https://agentfolio.bot)

Happy to contribute a trust-check middleware if there's interest.

The issue does not name any files, tests, or entry points beyond the mcp-x402 server that creates x402 payment headers. First clarify whether trust verification and a middleware integration are wanted, and agree on the trust provider, threshold behavior, and payment flow. Done would require an agreed implementation and tests covering proceed and reject decisions.

Written by the indexing model from the issue text.