Check a Base ERC-20 for a honeypot-style transfer cost before a swap or send. Input: one token address. Output: allow, warn, or block. Block: not a contract or not an ERC-20. Warn: bytecode contains taxFee, liquidityFee, sellFee, buyFee, transferFee, isBlacklisted, or maxTxAmount. USDC warns because it contains isBlacklisted(address). A selector does not prove the fee, blacklist, or cap runs on every transfer, and this check does not simulate one.