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/Nesting/MultiBinEngine.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CutList.Core.Nesting
+{
+    public class MultiBinEngine : IEngine
+    {
+        private readonly IEngineFactory _engineFactory;
+
+        public MultiBinEngine() : this(new EngineFactory())
+        {
+        }
+
+        public MultiBinEngine(IEngineFactory engineFactory)
+        {
+            _engineFactory = engineFactory ?? throw new ArgumentNullException(nameof(engineFactory));
+            _bins = new List<MultiBin>();
+        }
+
+        private readonly List<MultiBin> _bins;
+
+        /// <summary>
+        /// Gets the read-only collection of bins.
+        /// Use SetBins() to configure bins for packing.
+        /// </summary>
+        public IReadOnlyList<MultiBin> Bins => _bins.AsReadOnly();
+
+        /// <summary>
+        /// Sets the bins to use for packing.
+        /// </summary>
+        public void SetBins(IEnumerable<MultiBin> bins)
+        {
+            _bins.Clear();
+            if (bins != null)
+            {
+                _bins.AddRange(bins);
+            }
+        }
+
+        public double Spacing { get; set; }
+
+        public Result Pack(List<BinItem> items)
+        {
+            var bins = _bins
+                .Where(b => b.Length > 0)
+                .OrderBy(b => b.Priority)
+                .ThenBy(b => b.Length)
+                .ToList();
+
+            var result = new Result();
+            var remainingItems = new List<BinItem>(items);
+
+            foreach (var bin in bins)
+            {
+                var engine = _engineFactory.CreateEngine(bin.Length, Spacing, bin.Quantity);
+                var r = engine.Pack(remainingItems);
+
+                result.AddBins(r.Bins);
+                remainingItems = r.ItemsNotUsed.ToList();
+            }
+
+            result.AddItemsNotUsed(remainingItems);
+
+            return result;
+        }
+    }
+}