Function try_pick 

async fn try_pick(
    atlas: &mut AtlasClient,
    terminal: &mut Terminal<CrosstermBackend<Stdout>>,
    label: &str,
    contract: &str,
    kind: &str,
    saved_cap_id: Option<&str>,
    saved_device_id: Option<&str>,
    mode: PickMode,
) -> Result<Option<(String, String)>>

Ok(Some((provider_id, device_id))) = picked both layers; device_id may be “” when the impl returned UNIMPLEMENTED on list_devices. Ok(None) = no providers in atlas.