refactor: address S2365 collection-copying property getters

Resolves SonarQube S2365 x3.

CalculationFilterGroup (Snowflake + SqlServer): the `Filters` getter
ran .Where(...).ToList() on every access. Convert to a plain
auto-property holding the raw collection plus a `GetValidFilters()`
method that does the filtering. Update internal IsValid() and the two
QueryConfigExtensions callers to use the new method.

HierarchicalData.AllChildData: part of the IHierarchicalData interface
and JSON-serialized; the transformation IS the property's contract.
Suppress S2365 with justification rather than refactor -- same pattern
as S3875.

Behavior change: CalculationFilterGroup JSON output now serializes the
raw filter collection rather than the pre-filtered one. Round-trip is
preserved; callers needing the filtered view must call GetValidFilters().

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/Strata.SqlTools.SqlBreakdown/Expressions/InputPropertyExpression.cs

@@ -1,6 +1,7 @@
 using Strata.SqlTools.SqlBreakdown.Interfaces.Core;
 
 using System.Collections;
+using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Text.Json;
 using System.Text.Json.Serialization;
@@ -373,6 +374,7 @@ public class HierarchicalData : IHierarchicalData
 
     public IFlatData Data { get; set; }
 
+    [SuppressMessage("Major Code Smell", "S2365:Properties should not make collection or array copies", Justification = "AllChildData is part of the IHierarchicalData interface contract and is JSON-serialized (see Data.json). The flatten-on-get / group-on-set transformation is the deliberate purpose of the property — _childDataMap is the storage form, the property is the wire form.")]
     public IEnumerable<IHierarchicalData> AllChildData
     {
         get => _childDataMap.SelectMany(x => x.Value).ToList();