Same plain-list shape grid_spec() returns from a raster, plus grid_id and
lon360. When the grid's cell-id COG is on hand its geometry is read from the
file (authoritative, and keeps already-published v8 COGs bit-comparable, since
the real raster carries ~6e-6 deg of float drift from the nominal values); the
registry values are the offline fallback and are asserted against the raster.
Arguments
- grid_id
one of
grid_registry()$grid_id- cellid_tif
optional path to that grid's cell-id COG