Consider timing of writing metadata #60
Description
Currently, in write_zarr_array(), the .zarray metadata is written early, before the content is added to the chunks.
At the Zarr Summit 2025, it was flagged that this could be an issue if the zarr creation process failed halfway. We would have something that seems right: all the required files exist.
But the data would actually be incorrect.
Some other Zarr implementation do not write metadata until the very end to ensure there is a clear indication if Zarr data is corrupted.
Should we use the same approach? What are the other up-/downsides?