chore(sonar): bulk-fix mechanical CA/IDE analyzer warnings

Applied via `dotnet format analyzers --diagnostics IDE0028 CA1825 CA1834
CA1845 CA1847 CA1860 CA1866 CA1853 CA1830 CA1846 CA1806 CA1869 CA2249
--severity info`. 19 files touched, all mechanical syntactic rewrites:

- CA1847: string.Contains("x") -> string.Contains('x')
- CA2249: s.IndexOf(c) == -1 -> !s.Contains(c)
- CA1830: sb.Append(sb.ToString()) -> sb.Append(sb)
- CA1834: StringBuilder.Append("x") -> Append('x')
- CA1825, CA1860, CA1866, CA1853, IDE0028, CA1845: corresponding fixers

Three rules in the batch had no batch fixer available (CA1846 ×4,
CA1806 ×1, CA1869 ×1) and stay open for separate manual handling.

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

src/Strata.SqlTools.SqlBreakdown/Utilities/GuidUtils.cs

@@ -41,7 +41,7 @@ public static class GuidUtils
             return Guid.Empty;
         }
 
-        if (value.Contains("-"))
+        if (value.Contains('-'))
         {
             // This function was called on an already valid guid
             return new Guid(value);
@@ -92,7 +92,7 @@ public static class GuidUtils
         var sb = new System.Text.StringBuilder(newguid);
         while (sb.Length < Guid.Empty.ToString().Length)
         {
-            sb.Append(sb.ToString());
+            sb.Append(sb);
         }
         newguid = sb.ToString();
 
@@ -114,7 +114,7 @@ public static class GuidUtils
         for (int i = 0; i < guidChars.Length; i++)
         {
             char chr = guidChars[i];
-            if (valid.IndexOf(chr) == -1 && !((chr == '-') && (i == 8 || i == 13 || i == 18 || i == 23)))
+            if (!valid.Contains(chr) && !((chr == '-') && (i == 8 || i == 13 || i == 18 || i == 23)))
             {
                 guidChars[i] = valid[Math.Abs(StringUtils.GetHashCode32Bit(chr)) % valid.Length];
             }

src/Strata.SqlTools.SqlBreakdown/Utilities/SqlColumnHelpers.cs

@@ -16,7 +16,7 @@ public static partial class SqlUtils
     public static void AppendAliasColumnWithComma(StringBuilder stringBuilder, string alias, string columnName)
     {
         stringBuilder.Append(alias);
-        stringBuilder.Append(".");
+        stringBuilder.Append('.');
         stringBuilder.Append(columnName);
         stringBuilder.AppendLine(",");
     }
@@ -58,7 +58,7 @@ public static partial class SqlUtils
     {
         stringBuilder.Append("CAST(");
         stringBuilder.Append(alias);
-        stringBuilder.Append(".");
+        stringBuilder.Append('.');
         stringBuilder.Append(columnName);
         stringBuilder.Append(" AS ");
         stringBuilder.Append(dataType);
@@ -94,7 +94,7 @@ public static partial class SqlUtils
         {
             if (i > 0)
             {
-                sb.Append(",");
+                sb.Append(',');
             }
 
             string trimmed = columnNames[i].Trim();

src/Strata.SqlTools.SqlBreakdown/Utilities/SqlGuidHelpers.cs

@@ -42,10 +42,10 @@ public static partial class SqlUtils
 
         foreach (Guid g in guidList)
         {
-            sb.Append("'");
+            sb.Append('\'');
             sb.Append(g.ToString());
-            sb.Append("'");
-            sb.Append(",");
+            sb.Append('\'');
+            sb.Append(',');
         }
 
         return sb.ToString().Trim().TrimEnd(',');

src/Strata.SqlTools.SqlBreakdown/Utilities/SqlUtils.Filters.cs

@@ -27,7 +27,7 @@ public static partial class SqlUtils
         double.TryParse(value, out double dblValue);
 
         // Optimize IN if only one value
-        if (operation == FilterOperation.In && !value.Contains(","))
+        if (operation == FilterOperation.In && !value.Contains(','))
         {
             operation = FilterOperation.Equal;
         }
@@ -144,7 +144,7 @@ public static partial class SqlUtils
                 }
 
                 int lastCloseParen = sb.ToString().LastIndexOf(')');
-                filter.SqlExpression = sb.ToString().Substring(0, lastCloseParen + 1) + ")";
+                filter.SqlExpression = string.Concat(sb.ToString().AsSpan(0, lastCloseParen + 1), ")");
                 break;
 
             case FilterOperation.NotBetween: