Plain-list description of the global 0.05° -180,180 cell-id grid, so
publish_cog() can construct a windowed raster from a model's cell_ids
without serializing a terra SpatRaster across parallel workers. cell_id is
the row-major (top-left origin) 1-based cell index of this grid, so a cell's
row/col is pure arithmetic (no lookup against the COG).