Benchmark results and TODOs added / updated

EvenPerfectBitScanner.Benchmarks/Mod11UInt128Benchmarks.cs

@@ -11,16 +11,23 @@ public class Mod11UInt128Benchmarks
     [Params(11UL, 8191UL, 131071UL, 2147483647UL, ulong.MaxValue - 255UL)]
     public UInt128 Value { get; set; }
 
+    /// <summary>
+    /// Direct `% 11` for <see cref="UInt128"/>; ran in ~2.85-2.87 ns on every dataset (2.8719 ns at value 11, 2.8715 ns at 8191,
+    /// 2.8534 ns at 131071, 2.8716 ns at 2147483647, 2.8715 ns near ulong.Max).
+    /// </summary>
     [Benchmark(Baseline = true)]
     public ulong ModuloOperator()
     {
         return (ulong)(Value % 11UL);
     }
 
+    /// <summary>
+    /// Extension helper that folds digits with lookup coefficients; 0.66-0.68 ns across the inputs (0.6721 ns at value 11, 0.6765 ns
+    /// at 8191, 0.6760 ns at 131071, 0.6614 ns at 2147483647, 0.6661 ns near ulong.Max), about 4.2x faster than the baseline.
+    /// </summary>
     [Benchmark]
     public ulong ExtensionMethod()
     {
         return Value.Mod11();
     }
 }
-