Add TODOs for divisor metadata caching

PerfectNumbers.Core/CycleRemainderStepper.cs

@@ -36,6 +36,8 @@ internal struct CycleRemainderStepper
         ulong remainder = prime;
         if (remainder >= cycleLength)
         {
+            // TODO: Swap this `%` for the shared divisor-cycle remainder helper so initialization reuses the cached
+            // cycle deltas benchmarked faster than on-the-fly modulo work.
             remainder %= cycleLength;
         }
         _previousPrime = prime;
@@ -63,6 +65,8 @@ internal struct CycleRemainderStepper
         if (ulong.MaxValue - _currentRemainder < delta)
         {
             UInt128 extended = (UInt128)_currentRemainder + delta;
+            // TODO: Replace this `%` with the UInt128-aware cycle reducer so large deltas use the cached subtraction
+            // ladder instead of falling back to the slower modulo implementation.
             _currentRemainder = (ulong)(extended % cycleLength);
             return _currentRemainder;
         }
@@ -74,6 +78,8 @@ internal struct CycleRemainderStepper
             _currentRemainder -= cycleLength;
             if (_currentRemainder >= cycleLength)
             {
+                // TODO: Route this `%` through the shared divisor-cycle helper so repeated wrap-arounds avoid
+                // modulo operations and match the benchmarked fast path.
                 _currentRemainder %= cycleLength;
             }
         }