Get Evaluation Group Schema

Return a separate column schema for each active member evaluation of the group.

Rather than a single merged schema, the response holds one schema entry per active member evaluation (each with its field list, total item count, and sampling info), which lets a caller filter columns down to a chosen subset of the group’s evaluations. Schemas are computed from the member evaluations’ items; include_archived controls whether archived items are counted in that analysis. A group with no active members returns an empty schema list. This differs from the plain get endpoint, which returns group metadata and members but not their column schemas.