Function ensure_audio_devices 

async fn ensure_audio_devices(
    atlas_endpoint: &str,
    terminal: &mut Terminal<CrosstermBackend<Stdout>>,
) -> Result<(ChatConfig, Vec<String>)>

Best-effort audio device discovery. Anything that goes wrong here (atlas unreachable, no providers registered, user pressed Esc) is downgraded to a chat-history warning — text mode keeps working.