Function format_environment 

fn format_environment(
    os: &str,
    env: &EnvFacts,
    webview: &str,
    monitors: Option<&[MonitorFacts]>,
    local_now: &str,
    utc_offset: &str,
    build_profile: &str,
) -> String

Render the whole environment block from already-gathered facts. Pure: the caller does the env / windowing-system queries and passes the results in, so this formatting is fully unit-testable.