Explain order of consolidated metadata keys in user guide

Author: lkluft

docs/user-guide/consolidated_metadata.rst

@@ -100,6 +100,11 @@ With nested groups, the consolidated metadata is available on the children, recu
    >>> consolidated['child'].metadata.consolidated_metadata
    ConsolidatedMetadata(metadata={'child': GroupMetadata(attributes={'kind': 'grandchild'}, zarr_format=3, consolidated_metadata=ConsolidatedMetadata(metadata={}, kind='inline', must_understand=False), node_type='group')}, kind='inline', must_understand=False)
 
+The keys in the consolidated metadata are sorted in ascending order by path
+length, where a path is defined as a sequence of strings joined by '/'. For
+keys with the same path length, lexicographic order is used to break the tie.
+This behaviour ensures deterministic metadata output for a given group.
+
 Synchronization and Concurrency
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