Function project_diff 

pub async fn project_diff(
    api_a: &dyn GatewayApi,
    api_b: &dyn GatewayApi,
    project: &str,
    profile_a: &str,
    profile_b: &str,
) -> Result<ProjectDiffResult, CoreError>

ign project diff A B --project NAME — export both sides (A first), run the normalized member compare plus the project.json meta delta. A missing project on either side surfaces through export’s existing not-found path; the same profile twice is a usage-class refusal (exit 2) before any network I/O.