Function drift 

pub fn drift(
    manifest_path: &Path,
    dialect: &str,
    url: &str,
) -> Result<(), String>

fz tables drift: report, then fail when there was anything to report.

Drift is the finding, so it is also the exit code — a CI job asking “does this database still match the manifest?” needs an answer it can branch on rather than a paragraph it has to read.

Errors

Anything drift_report cannot do, and a summary line when the report was not empty.