Set the app-wide default panel render strategy for <cngx-tab-group>. Default 'eager' (every panel's content rendered up front, toggled
via [hidden]). 'lazy' keep-alives content after first activation;
'lazy-destroy' renders only the active panel's content. Per-instance
[panelMode] Input still wins. The panel <div> always stays in the
DOM regardless of mode (the aria-controls target).