Function validate_calls 

pub fn validate_calls(
    calls: &[Call],
    has_authorization_list: bool,
) -> Result<(), &'static str>

Validates the calls list structure for Tempo transactions.

This is a shared validation function used by both TempoTransaction::validate() and the revm handler’s validate_env() to ensure consistent validation.

Rules:

• Calls list must not be empty
• CREATE calls are not allowed when authorization list is non-empty (EIP-7702 semantics)
• Only the first call can be a CREATE; all subsequent calls must be CALL