docs: remove C# Implementation Considerations sections, clean up temp scripts, reorganize test files

- Remove 'C# Implementation Considerations' sections from 34 indicator .md files
- Delete 29 temp PowerShell scripts (_fix_mojibake.ps1, _hex_scan.ps1, etc.)
- Move test files into tests/ subdirectories for consistent project structure
- Add trader-focused bullet points to indicator documentation

lib/trends_FIR/sma/tests/Sma.ZeroDiv.Tests.cs

@@ -0,0 +1,33 @@
+
+namespace QuanTAlib.Tests;
+
+public class SmaZeroDivTests
+{
+    [Fact]
+    public void Sma_Update_WithIsNewFalse_OnEmptyBuffer_DoesNotThrow()
+    {
+        var sma = new Sma(10);
+
+        // Buffer is empty initially.
+        // Calling Update with isNew=false should not cause division by zero.
+        // It should return NaN or 0 or Last, but definitely not throw or return Infinity.
+
+        var result = sma.Update(new TValue(DateTime.UtcNow, 100), isNew: false);
+
+        // Since buffer count is 0, we expect NaN based on our fix.
+        Assert.True(double.IsNaN(result.Value), $"Expected NaN but got {result.Value}");
+    }
+
+    [Fact]
+    public void Sma_Update_WithIsNewFalse_AfterReset_DoesNotThrow()
+    {
+        var sma = new Sma(10);
+        sma.Update(new TValue(DateTime.UtcNow, 100));
+        sma.Reset();
+
+        // Buffer is empty after Reset.
+        var result = sma.Update(new TValue(DateTime.UtcNow, 200), isNew: false);
+
+        Assert.True(double.IsNaN(result.Value), $"Expected NaN but got {result.Value}");
+    }
+}