Add exact-zero guards in various classes to prevent division by zero errors

lib/cycles/cg/Cg.cs

@@ -180,6 +180,7 @@ public sealed class Cg : AbstractBase
     private double CalculateCg()
     {
         int n = _buffer.Count;
+        // skipcq: CS-R1077 - Exact-zero guard: _sum is cumulative price sum; zero means empty buffer, division by zero below
         if (n == 0 || _sum == 0)
         {
             return 0;
@@ -299,6 +300,7 @@ public sealed class Cg : AbstractBase
                 sum += price;
             }
 
+            // skipcq: CS-R1077 - Exact-zero guard: sum is cumulative price sum; zero means empty buffer, division by zero below
             if (sum == 0)
             {
                 output[i] = 0;

lib/cycles/homod/Homod.cs

@@ -321,6 +321,7 @@ public sealed class Homod : AbstractBase
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static double Atan2(double y, double x)
     {
+        // skipcq: CS-R1077 - Exact-zero guard: both quadrature components zero means no signal; atan2(0,0) is undefined
         if (y == 0.0 && x == 0.0)
         {
             return 0.0; // Return 0 instead of error for robustness

lib/cycles/ht_sine/HtSine.cs

@@ -206,9 +206,11 @@ public sealed class HtSine : AbstractBase
         prevI2 = i2;
 
         double tempReal1 = period;
+        // skipcq: CS-R1077 - Exact-zero guard: atan(im/re) requires nonzero denominator; zero im/re means no signal energy
         if (im != 0.0 && re != 0.0)
         {
             double angle = Math.Atan(im / re);
+            // skipcq: CS-R1077 - Exact-zero guard: angle == 0 means period is undefined (division by angle below)
             if (angle != 0.0)
             {
                 period = (2.0 * Math.PI) / angle;