feat(rsi, alma, bilateral, blma, butter, ema, htit, kama, lsma, pwma, rma, trima, vidya, wma): enhance calculations with NaN handling and edge case management; improve performance and stability across multiple classes

lib/trends/ema/Ema.Tests.cs

@@ -590,6 +590,21 @@ public class EmaTests
         Assert.Equal(verifyEma.Last.Value, indicator.Last.Value, 1e-10);
     }
 
+    [Fact]
+    public void Ema_Batch_AllNaNs_ReturnsNaN()
+    {
+        double[] source = [double.NaN, double.NaN, double.NaN];
+        double[] output = new double[3];
+        
+        Ema.Batch(source.AsSpan(), output.AsSpan(), 5);
+        
+        // Should be all NaNs, not 0s
+        foreach (var val in output)
+        {
+            Assert.True(double.IsNaN(val), $"Expected NaN but got {val}");
+        }
+    }
+
     [Fact]
     public void Ema_AllModes_ProduceSameResult()
     {

lib/trends/ema/Ema.cs

@@ -382,6 +382,7 @@ public sealed class Ema : AbstractBase
 
         var state = State.New();
         double lastValid = 0;
+        bool foundValid = false;
 
         // Find first valid value to seed lastValid
         for (int k = 0; k < source.Length; k++)
@@ -389,10 +390,17 @@ public sealed class Ema : AbstractBase
             if (double.IsFinite(source[k]))
             {
                 lastValid = source[k];
+                foundValid = true;
                 break;
             }
         }
 
+        if (!foundValid)
+        {
+            output.Fill(double.NaN);
+            return;
+        }
+
         CalculateCore(source, output, alpha, ref state, ref lastValid);
     }