Add Summary2 support for for hidden pages

### Description

If a layout page has the "hidden" property set to true, its values won’t appear in the Summary2 component that references it. Since most of our apps rely on prefilled XML data or a separate user input form, the components referenced by Summary2 shouldn't be visible to the end user.

### Additional Information

_No response_

Start by locating the Summary2 component and the layout-page handling for the "hidden" property. Verify how Summary2 currently includes referenced pages, then confirm that hidden pages remain available to prefilled XML or separate-form flows without appearing to end users.

Written by the indexing model from the issue text.