The reference layer is now in place

The reference layer is now in place as part of the docs launch. This creates a clearer separation between guides, update surfaces, and exact structured documentation.

Reference is where SGEN can document fields, settings, records, objects, and other exact definitions without turning every page into a long-form guide.

For the launch version, the important point is that this layer exists and gives the documentation system room to grow in a more organized way.