Canonicalize direct CDP x402 core

[EdgecaseSystems]

Summary

Keeps the sanitized portfolio snapshot internally correct at both layers instead of relying on the public wrapper to repair a known-obsolete core implementation:

• use the documented Coinbase CDP JWT claims directly in x402-core.ts
• bound the direct core payment-resource description to the same <=500-character compatibility description already used by the public boundary
• add a regression test that exercises the core directly and verifies there is no legacy iat/uris behavior

No credentials, operational identifiers, payment material, deployment data, or live tooling are added. This repository remains disconnected from production.