Function sign_safe_user_operation 

pub fn sign_safe_user_operation(
    signing_key: &SigningKey,
    environment: &PolyesterChainEnvironment,
    sender: &str,
    nonce: U256,
    init_code: &[u8],
    call_data: &[u8],
    call_gas_limit: u64,
    verification_gas_limit: u64,
    pre_verification_gas: u64,
    max_fee_per_gas: u64,
    max_priority_fee_per_gas: u64,
    paymaster_and_data: &[u8],
    valid_after: u64,
    valid_until: u64,
) -> Result<Vec<u8>>

EIP-712 SafeOp signature packed as uint48/uint48/bytes (single EOA owner).