Hybrid device mode implemented as the current --mersenne=bydivisor CPU execution path. CPU path is now limited to CPU calculations, only.

PerfectNumbers.Core/Cpu/MersenneNumberOrderCpuTester.cs

@@ -15,7 +15,7 @@ public class MersenneNumberOrderCpuTester(GpuKernelType kernelType)
 
 		while (k <= maxK && Volatile.Read(ref isPrime))
 		{
-			qCycle = MersenneDivisorCycles.GetCycle(gpu, q);
+			qCycle = MersenneDivisorCycles.GetCycleCpu(q);
 			// TODO: When this lookup misses the snapshot, invoke the configured device to compute the
 			// single required cycle on demand without persisting it so the CPU order path retains the
 			// cycle-stepping speedups while honoring the no-extra-cache constraint for large divisors.