Public API for determining if an array is sharded

[maxrjones]

Describe the new feature you'd like

Similar to #4035, it would simplify downstream use-cases to have a clear method that indicates if an array uses sharding.

Currently, one can use .shards is not None for regular chunk grids, but must use a try/except for sharded + rectilinear grids since the return type of .shards cannot express rectilinear grids.

See https://hackmd.io/p9pU24IQR6uA9tg6c0wMhw for a full evaluation of the API surface (generated by claude).

[d-v-b]

we could expose the ChunkLayout. When inner is None, no sharding codec is being used. We would need to update this to accommodate any new codecs that implement sharding.

[maxrjones]

we could expose the ChunkLayout. When inner is None, no sharding codec is being used. We would need to update this to accommodate any new codecs that implement sharding.

would it be better to expose ChunkLayout via Zarr's regular API or a metadata package?

[d-v-b]

I don't think it belongs in a metadata package, since it's something we invented for an internal representation in zarr-python. it's basically a distillation of the chunk grid + codecs for an array, so it's could be useful as an attribute on array metadata, or on the array itself. we might need to polish it a bit, e.g. changing field names

[maxrjones]

I don't think it belongs in a metadata package, since it's something we invented for an internal representation in zarr-python. it's basically a distillation of the chunk grid + codecs for an array, so it's could be useful as an attribute on array metadata, or on the array itself. we might need to polish it a bit, e.g. changing field names

makes sense.

A ChunkLayout attribute could be a logical place to solve #4035 as well.