Add TODOs for divisor metadata caching

PerfectNumbers.Core/Gpu/MersenneNumberResidueGpuTester.cs

@@ -24,7 +24,7 @@ public class MersenneNumberResidueGpuTester(bool useGpuOrder)
                 UInt128 kStart = 1UL;
                 UInt128 limit = maxK + UInt128.One;
 		byte last = lastIsSeven ? (byte)1 : (byte)0;
-		var kernel = gpuLease.Pow2ModKernel;
+                var kernel = gpuLease.Pow2ModKernel; // TODO: Swap this to the ProcessEightBitWindows kernel once GpuUInt128.Pow2Minus1Mod adopts the shared windowed helper measured fastest in GpuPow2ModBenchmarks.
                 twoP.Mod10_8_5_3(out ulong step10, out ulong step8, out ulong step5, out ulong step3);
                 step10 = step10.Mod10();