});
    /* the stream listener is still allowed to have nothing behind it (a
       desktop build, the mock without the bus); the transport's failure is
       still the one the shell shows, and the unlisten handed back is still
       the transport's — the one onMount stores and calls on teardown. */
    const [, unlisten] = await Promise.all([streamSub.catch(() => { /* not a phone */ }), transportSub]);
    return unlisten;
}