Authoritative shards (shard catalog alignment) checks in checkMetadataConsistency currently omit severity.

The field is optional and only config.system.sessions UUID/options mismatches set low; every authoritative shards type (i.e. InconsistentShardCatalogCollectionMetadata) is returned with no severity at all.

We need to set an explicit non-low severity on all new authoritative shards checks items so they stay a real correctness signal and cannot be treated as ignorable.