feat: add PairCandidate, BestFitResult, and IBestFitStrategy for best-fit pair finding

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

OpenNest.Engine/BestFit/BestFitResult.cs

@@ -0,0 +1,40 @@
+namespace OpenNest.Engine.BestFit
+{
+    public class BestFitResult
+    {
+        public PairCandidate Candidate { get; set; }
+        public double RotatedArea { get; set; }
+        public double BoundingWidth { get; set; }
+        public double BoundingHeight { get; set; }
+        public double OptimalRotation { get; set; }
+        public bool Keep { get; set; }
+        public string Reason { get; set; }
+        public double TrueArea { get; set; }
+
+        public double Utilization
+        {
+            get { return RotatedArea > 0 ? TrueArea / RotatedArea : 0; }
+        }
+
+        public double LongestSide
+        {
+            get { return System.Math.Max(BoundingWidth, BoundingHeight); }
+        }
+
+        public double ShortestSide
+        {
+            get { return System.Math.Min(BoundingWidth, BoundingHeight); }
+        }
+    }
+
+    public enum BestFitSortField
+    {
+        Area,
+        LongestSide,
+        ShortestSide,
+        Type,
+        OriginalSequence,
+        Keep,
+        WhyKeepDrop
+    }
+}

OpenNest.Engine/BestFit/IBestFitStrategy.cs

@@ -0,0 +1,11 @@
+using System.Collections.Generic;
+
+namespace OpenNest.Engine.BestFit
+{
+    public interface IBestFitStrategy
+    {
+        int Type { get; }
+        string Description { get; }
+        List<PairCandidate> GenerateCandidates(Drawing drawing, double spacing, double stepSize);
+    }
+}

OpenNest.Engine/BestFit/PairCandidate.cs

@@ -0,0 +1,15 @@
+using OpenNest.Geometry;
+
+namespace OpenNest.Engine.BestFit
+{
+    public class PairCandidate
+    {
+        public Drawing Drawing { get; set; }
+        public double Part1Rotation { get; set; }
+        public double Part2Rotation { get; set; }
+        public Vector Part2Offset { get; set; }
+        public int StrategyType { get; set; }
+        public int TestNumber { get; set; }
+        public double Spacing { get; set; }
+    }
+}

OpenNest.Engine/OpenNest.Engine.csproj

@@ -37,6 +37,9 @@
   </ItemGroup>
   <ItemGroup>
     <Compile Include="BestCombination.cs" />
+    <Compile Include="BestFit\PairCandidate.cs" />
+    <Compile Include="BestFit\BestFitResult.cs" />
+    <Compile Include="BestFit\IBestFitStrategy.cs" />
     <Compile Include="CirclePacking\Bin.cs" />
     <Compile Include="CirclePacking\FillEndEven.cs" />
     <Compile Include="CirclePacking\FillEndOdd.cs" />