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>

src/Strata.SqlTools.SqlServer/Statements/StatementParser.cs

@@ -21,6 +21,7 @@ public class StatementParser
     public const string KeywordGroupBy = "GROUP BY";
     public const string KeywordHaving = "HAVING";
     public const string KeywordOrderBy = "ORDER BY";
+    private static readonly char[] separator = new[] { '\r', '\n' };
 
     #endregion
 
@@ -50,7 +51,7 @@ public class StatementParser
         // Replace multiple spaces/tabs with single space, but preserve newlines for comment handling
         sql = Regex.Replace(sql, @"[ \t]+", " ", RegexOptions.None, RegexDefaults.MatchTimeout);
         // Remove leading/trailing whitespace from each line
-        var lines = sql.Split(new[] { '\r', '\n' }, StringSplitOptions.None);
+        var lines = sql.Split(separator, StringSplitOptions.None);
         sql = string.Join("\n", lines.Select(line => line.Trim()));
         return sql.Trim();
     }