Paid agent-facing brief on x402 challenge payability and payment-scheme compatibility check: agent-side procedure that g

Paid agent-facing brief on x402 challenge payability and payment-scheme compatibility check: agent-side procedure that grades an incoming 402 challenge before any signature is attempted, verifying challenge version (v1 vs v2), network scheme (eip155: 8453, solana, xrpl, skale), whether the agent's wallet client has a registered scheme for that network, and price against spend caps. Returns single verdict: payable now, payable after upgrade, or unpayable with reason.. Blunt decision procedure,