Function startup_banner 

fn startup_banner(
    version: &str,
    os: &str,
    display: &str,
    webview: &str,
    monitor_count: usize,
    idle: &Result<u64, String>,
    wlfix: &str,
) -> String

Compact one-line environment summary logged once at startup, so the log file (and therefore every diagnostics report’s log tail) always opens with the context a bug report needs — even if the user never generates a report. Pure so the formatting is unit-testable.