Validation

This implements ERC-8004 on-chain agent validation for Stacks L2, letting agents request validation from validators and letting validators respond with scored assessments. You get six subcommands: request and respond for write operations (which need a wallet), plus four read operations for checking status, pulling summaries, and paginating through validation lists by agent or validator. Responses are 0-100 scores that can be updated progressively, all tied to SHA-256 hashes of request and response data. The pagination works with 14-item pages and cursor-based navigation. If you're building agent reputation systems or need verifiable on-chain trust signals, this gives you the primitives to do it without rolling your own registry contract.