Rename SawCut library to CutList.Core

Rename the core library project from SawCut to CutList.Core for consistent
branding across the solution. This includes:
- Rename project folder and .csproj file
- Update namespace from SawCut to CutList.Core
- Update all using statements and project references

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CutList.Core/Bin.cs

@@ -0,0 +1,79 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CutList.Core
+{
+    public class Bin
+    {
+        private readonly List<BinItem> _items;
+
+        public Bin(double length)
+        {
+            _items = new List<BinItem>();
+            Length = length;
+        }
+
+        public IReadOnlyList<BinItem> Items => _items;
+
+        public void AddItem(BinItem item)
+        {
+            _items.Add(item);
+        }
+
+        public void AddItems(IEnumerable<BinItem> items)
+        {
+            _items.AddRange(items);
+        }
+
+        public void RemoveItem(BinItem item)
+        {
+            _items.Remove(item);
+        }
+
+        public void SortItems(Comparison<BinItem> comparison)
+        {
+            _items.Sort(comparison);
+        }
+
+        public double Spacing { get; set; }
+
+        public double Length { get; set; }
+
+        public double UsedLength
+        {
+            get
+            {
+                var usedLength = Math.Round(Items.Sum(i => i.Length) + Spacing * Items.Count, 8);
+
+                if (usedLength > Length && (usedLength - Length) <= Spacing)
+                    return Length;
+
+                return Math.Round(Items.Sum(i => i.Length) + Spacing * Items.Count, 8);
+            }
+        }
+
+        public double RemainingLength
+        {
+            get { return Math.Round(Length - UsedLength, 8); }
+        }
+
+        /// <summary>
+        /// Returns a ratio of UsedLength to TotalLength
+        /// 1.0 = 100% utilization
+        /// </summary>
+        public double Utilization
+        {
+            get { return UsedLength / Length; }
+        }
+
+        public override string ToString()
+        {
+            var totalLength = FormatHelper.ConvertToMixedFraction(Math.Round(Length, 4));
+            var remainingLength = FormatHelper.ConvertToMixedFraction(Math.Round(RemainingLength, 4));
+            var utilitation = Math.Round(Utilization * 100, 2);
+
+            return $"Length: {totalLength}, {remainingLength} remaining, {Items.Count} items, {utilitation}% utilization";
+        }
+    }
+}