Function resolve_default_browser 

pub fn resolve_default_browser(
    platform: &str,
    environment: &Environment,
    run_command: &RunCommand,
) -> Result<Option<&'static str>>

Resolve the system default browser to a canonical catalogue id, or None when it cannot be determined. On macOS a failure of the lookup tool propagates as an error (there is no fallback); on Linux and Windows a missing tool resolves to None.