docs: update category index files and fix indicator implementations (#58)

lib/filters/sgf/Sgf.Validation.Tests.cs

@@ -113,10 +113,7 @@ public class SgfValidationTests : IDisposable
             if (wSum <= double.Epsilon)
             {
                 int availablePoints = Math.Min(i + 1, adjPeriod);
-                if (availablePoints < adjPeriod)
-                    result[i] = source[i];
-                else
-                    result[i] = double.NaN;
+                result[i] = availablePoints < adjPeriod ? source[i] : double.NaN;
             }
         }
 
@@ -202,4 +199,4 @@ public class SgfValidationTests : IDisposable
         }
         _output.WriteLine("Span mode successfully validated against reference implementation");
     }
-}
+}

lib/filters/sgf/Sgf.cs

@@ -248,11 +248,8 @@ public sealed class Sgf : AbstractBase
             }
             else
             {
-                // If wSum is zero/negative/small
-                if (count < adjPeriod)
-                    output[i] = source[i]; // Pass through for partial window
-                else
-                    output[i] = double.NaN;
+                // If wSum is zero/negative/small - pass through for partial window, else NaN
+                output[i] = count < adjPeriod ? source[i] : double.NaN;
             }
         }
     }