Fix final 2 CodeQL alerts

HicServices#28 WARNING: Fixed Equals pattern to handle subclasses correctly
- Changed from 'is' pattern to GetType() comparison in DecimalSize.Equals(object)
- This ensures proper equality behavior for potential subclasses

#1 NOTE: Extracted Where filter to separate variable in DateTimeTypeDecider
- Moved Where clause to explicit variable before foreach
- Satisfies CodeQL recommendation while avoiding ref struct limitation

Build: 0 warnings, 0 errors. Tests: 377/377 passing.

Author: jas88

TypeGuesser/Deciders/DateTimeTypeDecider.cs

@@ -205,7 +205,9 @@ public void GuessDateFormat(IEnumerable<string> samples)
         if (!AllowCultureGuessing)
             return;
 
-        foreach (var sSample in samples.Where(static sSample => !string.IsNullOrWhiteSpace(sSample)))
+        var nonEmptySamples = samples.Where(static s => !string.IsNullOrWhiteSpace(s));
+
+        foreach (var sSample in nonEmptySamples)
         {
             var sample = sSample.AsSpan();
             total++;

TypeGuesser/DecimalSize.cs

@@ -144,7 +144,10 @@ public bool Equals(DecimalSize? other)
     /// <inheritdoc/>
     public override bool Equals(object? obj)
     {
-        return obj is DecimalSize other && Equals(other);
+        if (obj is null) return false;
+        if (ReferenceEquals(this, obj)) return true;
+        // Use GetType() comparison to handle subclasses correctly
+        return obj.GetType() == GetType() && Equals((DecimalSize)obj);
     }
 
     /// <inheritdoc/>