Method ExecuteTreeGroupedAggregateAsync<TProps>(TreeQueryContext<TProps>, IEnumerable<GroupFieldRequest>, IEnumerable<AggregateRequest>)

ITreeQueryProvider implementation: Execute GROUP BY with tree context.
Uses CTE for tree traversal + PVT for efficient field access.

public override Task<JsonDocument?> ExecuteTreeGroupedAggregateAsync<TProps>(TreeQueryContext<TProps> context, IEnumerable<GroupFieldRequest> groupFields, IEnumerable<AggregateRequest> aggregations) where TProps : class, new()