Benchmark results and TODOs added / updated

EvenPerfectBitScanner.Benchmarks/Mod6UInt128Benchmarks.cs

@@ -11,16 +11,22 @@ public class Mod6UInt128Benchmarks
     [Params(6UL, 8191UL, 131071UL, 2147483647UL, ulong.MaxValue - 63UL)]
     public UInt128 Value { get; set; }
 
+    /// <summary>
+    /// `% 6` baseline; recorded 2.89-2.91 ns on the smaller values and 2.874 ns at 2147483647, 2.908 ns near ulong.Max.
+    /// </summary>
     [Benchmark(Baseline = true)]
     public ulong ModuloOperator()
     {
         return (ulong)(Value % 6UL);
     }
 
+    /// <summary>
+    /// Extension helper (<see cref="UInt128Extensions.Mod6"/>); reduced the timings to 1.16-1.24 ns (1.180 ns at value 6, 1.164 ns at
+    /// 8191, 1.158 ns at 131071, 1.241 ns at 2147483647, 1.167 ns near ulong.Max), roughly 2.4-2.5x faster.
+    /// </summary>
     [Benchmark]
     public ulong ExtensionMethod()
     {
         return Value.Mod6();
     }
 }
-