fix(nucleus): track cell portals

apis/nucleus/src/components/boot.jsx

@@ -6,6 +6,7 @@ export default function boot({ element, model, api, nebulaContext, onInitial })
   const { root } = nebulaContext;
 
   const portal = ReactDOM.createPortal(<Cell api={api} model={model} onInitial={onInitial} />, element);
+  portal.key = model.id; // TODO - handle same model being booted again
 
   const unmount = () => {
     root.remove(portal);