Anchors the psychology atlas's own top-level category entities, one per major entity type the atlas tracks: psychologist, theory, study, school, branch, source, subcategory, relation-type and open-question. The grouping is by entity type itself, not by subject matter, and exists so each type has its own browsable landing page. It deliberately excludes the psychological subjects those types describe: a specific psychologist, theory or study lives under its own type's category, never under this meta-level page, which lists the category structure itself rather than the atlas's substantive content.