fix: over-rounding on negative midpoint values

Author: mrdav30

src/FixedMathSharp/Core/FixedMath.cs

@@ -176,7 +176,7 @@ public static Fixed64 Round(Fixed64 value, MidpointRounding mode = MidpointRound
             // When value is exactly Fixed64.Halfway between two numbers
             return mode switch
             {
-                MidpointRounding.AwayFromZero => value.m_rawValue > 0 ? integralPart + Fixed64.One : integralPart - Fixed64.One,// If it's exactly Fixed64.Halfway, round away from Fixed64.Zero
+                MidpointRounding.AwayFromZero => value.m_rawValue > 0 ? integralPart + Fixed64.One : integralPart,// For negative midpoints, Floor() is already away from zero
                 _ => (integralPart.m_rawValue & ONE_L) == 0 ? integralPart : integralPart + Fixed64.One,// Rounds to the nearest even number (default behavior)
             };
         }
@@ -366,4 +366,4 @@ public static long AddOverflowHelper(long x, long y, ref bool overflow)
 
         #endregion
     }
-}
+}