ERC-8366 Standardizes Private Agent Spending Policies

New ERC standardizes zero-knowledge spending policies for agent payments. One policy authorizes one settlement, capping damage. ERC-7715 and ERC-7710 enforce public limits; this keeps parameters private via commitment. Proofs bind off-chain facts like signed quotes via verifyPolicy and ERC-1271 adapter. Spender, contract or EOA, needs no per-payment signature.