I don't think there's a good objective metric here, at least not like cyclomatic complexity or SonarQube-style checks, because it's difficult to tell whether the code is overcomplicated by AI, or whether the domain itself is just complicated.
Code is derivative - it's modeling real behavior. So its quality depends closely on how well it captures what should actually happen.
That's why measuring the actual outcome is more important than raw "code quality" metrics: do the important user flows and edge cases work, how the system behaves in these edge cases. I'd more use something like Journey SDK to fuzz edge cases and measure how well the system behaves, rather than measure some arbitrary properties of the code.