Add support for x402 v2

[madars]

radius-cli 0.1.4 speaks x402 v1 only; can't pay v2 / Permit2 tokens (e.g. SBC). Against an x402 v2 resource server it: reads the 402 body instead of the PAYMENT-REQUIRED header; requires maxAmountRequired (v2 uses amount); sends X-PAYMENT (v2 uses PAYMENT-SIGNATURE); emits a payload missing accepted with numeric validAfter/validBefore (v2 wants strings); and signs EIP-3009, so it fails against tokens that require EIP-2612+Permit2 — including Radius testnet SBC (facilitator returns "EIP-3009 … not supported … use EIP-2612 (permit) instead").

Ask: support x402 v2 transport + honor extra.assetTransferMethod: permit2 when advertised.

[erikzrekz]

Resolved by merged PR #17 (commit 27b408a): #17

The CLI now supports the requested x402 v2 behavior: it reads the v2 PAYMENT-REQUIRED header, normalizes v2 amount, sends PAYMENT-SIGNATURE, emits the v2 accepted envelope with stringified numeric fields, and selects Permit2 when accepts[].extra.assetTransferMethod is permit2. Existing x402 v1 support remains intact.

Validation recorded in PR #17: npm test 56/56, build passing, and successful live v2 Permit2 exact/upto settlements on Radius testnet SBC and mainnet USDC. Closing as resolved.