Document GPU kernel audit progress

PerfectNumbers.Core/Gpu/Kernels/SmallPrimeFactorKernels.cs

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+using ILGPU;
+using ILGPU.Runtime;
+
+namespace PerfectNumbers.Core.Gpu;
+
+internal static class SmallPrimeFactorKernels
+{
+    public static void SmallPrimeFactorKernelScan(
+        Index1D index,
+        ulong value,
+        uint limit,
+        ArrayView1D<uint, Stride1D.Dense> primes,
+        ArrayView1D<ulong, Stride1D.Dense> squares,
+        int primeCount,
+        ArrayView1D<ulong, Stride1D.Dense> primeSlots,
+        ArrayView1D<int, Stride1D.Dense> exponentSlots,
+        ArrayView1D<int, Stride1D.Dense> countSlot,
+        ArrayView1D<ulong, Stride1D.Dense> remainingSlot)
+    {
+        if (index != 0)
+        {
+            return;
+        }
+
+        uint effectiveLimit = limit == 0 ? uint.MaxValue : limit;
+        ulong remaining = value;
+        int count = 0;
+        int capacity = (int)primeSlots.Length;
+
+        for (int i = 0; i < primeCount && remaining > 1UL && count < capacity; i++)
+        {
+            uint primeCandidate = primes[i];
+            if (primeCandidate == 0U || primeCandidate > effectiveLimit)
+            {
+                break;
+            }
+
+            ulong primeSquare = squares[i];
+            if (primeSquare != 0UL && primeSquare > remaining)
+            {
+                break;
+            }
+
+            ulong primeValue = primeCandidate;
+            if ((remaining % primeValue) != 0UL)
+            {
+                continue;
+            }
+
+            int exponent = 0;
+            do
+            {
+                remaining /= primeValue;
+                exponent++;
+            }
+            while ((remaining % primeValue) == 0UL);
+
+            primeSlots[count] = primeValue;
+            exponentSlots[count] = exponent;
+            count++;
+        }
+
+        countSlot[0] = count;
+        remainingSlot[0] = remaining;
+    }
+}