feat: support viem token sets

[brendanjryan]

Motivation

Allow EVM and x402 payment config to reuse viem token definitions and token sets for currency resolution and allowlists.

Summary

• Added shared x402 asset helpers for viem token definitions and token-set currency matching
• Allowed EVM/x402 client currency policies and EVM server currency config to accept viem tokens
• Added focused runtime/type coverage and a patch changeset

Key design considerations

• Kept EIP-3009 version explicit for viem tokens because viem token metadata does not include transfer version
• Preserved the raw-address network requirement while allowing token definitions to resolve by challenge network
• Rejected known assets configured against a mismatched chain ID instead of producing inconsistent challenges

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/mppx@608

commit: 57e408d