chore(sonar): hoist constant array literals to static readonly fields (CA1861)

Applied via `dotnet format analyzers --diagnostics CA1861 --severity info`,
plus manual cleanup:

- Renamed two cryptic fixer-generated field names:
  - QueryBreakdownCollection.stringArray -> SnowflakeFunctionNames (and
    inlined the now-redundant local alias)
  - ExpressionObjectTests.arg2 -> NotInValues
- Deduped three identical `separator = ['\r','\n']` fields the fixer
  emitted in the same test class (kept the first declaration; the other
  two test methods now reuse it).

8 files touched.

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

tests/Strata.SqlTools.SqlBreakdown.Tests/Extensions/QueryBreakdownExtensionsTests.cs

@@ -243,12 +243,14 @@ public class QueryBreakdownExtensionsTests
         Assert.That(query.WithClauses[1].TableName, Is.EqualTo("recent_orders"));
     }
 
+    private static readonly string[] columns = new[] { "id", "name", "email" };
+
     [Test]
     public void WithCte_WithColumnList_AddsCtesWithColumns()
     {
         // Arrange & Act
         var query = new QueryBreakdown()
-            .WithCte("active_users", new[] { "id", "name", "email" }, cte => cte
+            .WithCte("active_users", columns, cte => cte
                 .Select("user_id, user_name, user_email")
                 .From("users")
                 .Where("status = 'active'"))