Get Layer Features Paginated

Response for the paginated sandbox query endpoint.

last_row is the exact filtered match count, computed alongside the page via a single windowed COUNT(*) OVER(). AG Grid uses it to size the scrollbar.

matched_rows and total_rows are the footer's "X of Y", sent together or not at all. Both are measured on one request against one relation, so a client that renders them as a pair can never combine counts drawn from different layers or from different moments in the layer's life. They are present only on a request whose counts describe the whole layer — a first page with no group_keys; a later page repeats a count the first already carried, and a child block counts one group. matched_rows is null on a grouped request, whose last_row counts groups and so has nothing comparable to total_rows.

This shape is deliberately reconciled server-side: a client that re-derived "is this the footer's request?" from the request params would be a second copy of that rule, free to drift from this one.