Function check 

pub fn check(
    config_dir: &Path,
    force: bool,
) -> Result<Option<UpdateStatus>, UpdateError>

Check for an update (blocking — prefer the async check_now).

When force is false the check is throttled: if the cached result is fresh (< [CHECK_INTERVAL_HOURS]) no network call is made and the cached version is reused. force (manual check / kimun update) always queries GitHub.

Returns Ok(None) only when throttled with no cached version yet.