Refactor Helper to FormatHelper with improved documentation

- Rename Helper class to FormatHelper for clarity
- Add comprehensive XML documentation
- Update all references in BinFileSaver, ArchUnits, and Bin
- Remove unused System.Drawing import
- Better method documentation explaining parameters and return values

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

SawCut/FormatHelper.cs

@@ -0,0 +1,62 @@
+using System;
+
+namespace SawCut
+{
+    /// <summary>
+    /// Provides formatting utilities for displaying measurements and values.
+    /// </summary>
+    public static class FormatHelper
+    {
+        /// <summary>
+        /// Converts a decimal measurement to a mixed fraction string representation.
+        /// </summary>
+        /// <param name="input">The decimal value to convert</param>
+        /// <param name="precision">The denominator precision (default 32 for 1/32")</param>
+        /// <returns>A string in the format "whole-numerator/denominator"</returns>
+        public static string ConvertToMixedFraction(decimal input, int precision = 32)
+        {
+            // Get the whole number part
+            int wholeNumber = (int)input;
+
+            // Get the fractional part
+            decimal fractionalPart = Math.Abs(input - wholeNumber);
+
+            if (fractionalPart == 0)
+            {
+                return wholeNumber.ToString();
+            }
+
+            // Convert the fractional part to a fraction
+            int numerator = (int)(fractionalPart * precision);
+            int denominator = precision;
+
+            // Simplify the fraction
+            int gcd = GetGreatestCommonDivisor(numerator, denominator);
+            numerator /= gcd;
+            denominator /= gcd;
+
+            return $"{wholeNumber}-{numerator}/{denominator}";
+        }
+
+        /// <summary>
+        /// Converts a double measurement to a mixed fraction string representation.
+        /// </summary>
+        /// <param name="input">The double value to convert</param>
+        /// <returns>A string in the format "whole-numerator/denominator"</returns>
+        public static string ConvertToMixedFraction(double input)
+        {
+            return ConvertToMixedFraction((decimal)input);
+        }
+
+        private static int GetGreatestCommonDivisor(int a, int b)
+        {
+            while (b != 0)
+            {
+                int temp = b;
+                b = a % b;
+                a = temp;
+            }
+            return Math.Abs(a);
+        }
+    }
+}