Select time slices of a stacked raster or a dataset by label.
time_sel.RdLabel selection on the t axis (the .sel(time = ...) analog):
each selector matches its exact label, or failing that every label it
prefixes ("2023-06" selects every June slice); the matches are
combined. Integer/logical positions work too. A selector that matches
nothing is an error.
A raster must be a lazy_stack along t whose layers were named
(slice dates); a single match returns the bare layer. A dataset keeps
the matching slices of every band (each band's slices are labelled by
date, or by the time coordinate of an N-D source such as a Zarr array).