A single bin record from byColumn — its [start, end) range plus the mapped
aggregate columns (read by name via stacksFromBins). Deliberately just
the start/end shape (no index signature) so pond's
byColumn(...): Array<{ start, end } & ReduceResult> assigns to it structurally
— the aggregate fields ride along and are read out by the reader.
A single bin record from
byColumn— its[start, end)range plus the mapped aggregate columns (read by name via stacksFromBins). Deliberately just thestart/endshape (no index signature) so pond'sbyColumn(...): Array<{ start, end } & ReduceResult>assigns to it structurally — the aggregate fields ride along and are read out by the reader.