Keikai theme contains rules affecting default ZK theme components

Steps to Reproduce

Run keikai 5.3.0 with ZK 9.1.0

Add a component using font-awesome icons (bandbox, combobox, searchbox, etc)

<zk>
    <bandbox/>
    <searchbox/>
    <zscript><![CDATA[
        ListModelList model = new ListModelList(Locale.getAvailableLocales());
        ListSubModel subModel = ListModels.toListSubModel(model);
    ]]></zscript>
    <chosenbox width="400px" model="${subModel}"/>
</zk>

Current Result

loading the keikai dependency affect the theme of pure ZK pages (no keikai component in this zul file)

Expected Result

loading keikai dependency shouldn't affect pure ZK page theme

Debug Information

likely affected by keikai less files:

https://github.com/zkoss/keikaicml/blob/1175fecd450c1ecfee3236a520f89ca58546afe7/keikai/src/archive/web/js/zss/less/_mixins.less#L11

https://github.com/zkoss/keikaicml/blob/1175fecd450c1ecfee3236a520f89ca58546afe7/keikai/src/archive/web/js/zss/less/_zkmixins.less#L293

Workaround