feat: wire IFillComparer through FillHelpers, Linear, and Extents strategies

- FillHelpers.FillPattern gains optional IFillComparer parameter; falls back to FillScore when null
- LinearFillStrategy.Fill replaced with FillWithDirectionPreference + comparer from context.Policy
- ExtentsFillStrategy.Fill replaced with comparer.IsBetter, removing FillScore comparison
- DefaultNestEngine group-fill path resolves Task 6 TODO, passing Comparer to FillPattern

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

OpenNest.Engine/DefaultNestEngine.cs

@@ -89,8 +89,7 @@ namespace OpenNest
             PhaseResults.Clear();
             var engine = new FillLinear(workArea, Plate.PartSpacing);
             var angles = RotationAnalysis.FindHullEdgeAngles(groupParts);
-            // TODO: pass Comparer to FillPattern (Task 6)
+            var best = FillHelpers.FillPattern(engine, groupParts, angles, workArea, Comparer);
-            var best = FillHelpers.FillPattern(engine, groupParts, angles, workArea);
             PhaseResults.Add(new PhaseResult(NestPhase.Linear, best?.Count ?? 0, 0));
 
             Debug.WriteLine($"[Fill(groupParts,Box)] Linear pattern: {best?.Count ?? 0} parts | WorkArea: {workArea.Width:F1}x{workArea.Length:F1}");

OpenNest.Engine/Strategies/ExtentsFillStrategy.cs

@@ -21,7 +21,7 @@ namespace OpenNest.Engine.Strategies
             var angles = new[] { bestRotation, bestRotation + Angle.HalfPI };
 
             List<Part> best = null;
-            var bestScore = default(FillScore);
+            var comparer = context.Policy?.Comparer ?? new DefaultFillComparer();
 
             foreach (var angle in angles)
             {
@@ -30,12 +30,8 @@ namespace OpenNest.Engine.Strategies
                     context.PlateNumber, context.Token, context.Progress);
                 if (result != null && result.Count > 0)
                 {
-                    var score = FillScore.Compute(result, context.WorkArea);
+                    if (best == null || comparer.IsBetter(result, best, context.WorkArea))
-                    if (best == null || score > bestScore)
-                    {
                         best = result;
-                        bestScore = score;
-                    }
                 }
             }
 

OpenNest.Engine/Strategies/FillHelpers.cs

@@ -30,7 +30,7 @@ namespace OpenNest.Engine.Strategies
             return pattern;
         }
 
-        public static List<Part> FillPattern(FillLinear engine, List<Part> groupParts, List<double> angles, Box workArea)
+        public static List<Part> FillPattern(FillLinear engine, List<Part> groupParts, List<double> angles, Box workArea, IFillComparer comparer = null)
         {
             var results = new ConcurrentBag<(List<Part> Parts, FillScore Score)>();
 
@@ -55,10 +55,18 @@ namespace OpenNest.Engine.Strategies
 
             foreach (var res in results)
             {
-                if (best == null || res.Score > bestScore)
+                if (comparer != null)
                 {
-                    best = res.Parts;
+                    if (best == null || comparer.IsBetter(res.Parts, best, workArea))
-                    bestScore = res.Score;
+                        best = res.Parts;
+                }
+                else
+                {
+                    if (best == null || res.Score > bestScore)
+                    {
+                        best = res.Parts;
+                        bestScore = res.Score;
+                    }
                 }
             }
 

OpenNest.Engine/Strategies/LinearFillStrategy.cs

@@ -17,8 +17,9 @@ namespace OpenNest.Engine.Strategies
                 : new List<double> { 0, Angle.HalfPI };
 
             var workArea = context.WorkArea;
+            var comparer = context.Policy?.Comparer ?? new DefaultFillComparer();
+            var preferred = context.Policy?.PreferredDirection;
             List<Part> best = null;
-            var bestScore = default(FillScore);
 
             for (var ai = 0; ai < angles.Count; ai++)
             {
@@ -26,48 +27,29 @@ namespace OpenNest.Engine.Strategies
 
                 var angle = angles[ai];
                 var engine = new FillLinear(workArea, context.Plate.PartSpacing);
-                var h = engine.Fill(context.Item.Drawing, angle, NestDirection.Horizontal);
+
-                var v = engine.Fill(context.Item.Drawing, angle, NestDirection.Vertical);
+                var result = FillHelpers.FillWithDirectionPreference(
+                    dir => engine.Fill(context.Item.Drawing, angle, dir),
+                    preferred, comparer, workArea);
 
                 var angleDeg = Angle.ToDegrees(angle);
 
-                if (h != null && h.Count > 0)
+                if (result != null && result.Count > 0)
                 {
-                    var scoreH = FillScore.Compute(h, workArea);
                     context.AngleResults.Add(new AngleResult
                     {
                         AngleDeg = angleDeg,
-                        Direction = NestDirection.Horizontal,
+                        Direction = preferred ?? NestDirection.Horizontal,
-                        PartCount = h.Count
+                        PartCount = result.Count
                     });
 
-                    if (best == null || scoreH > bestScore)
+                    if (best == null || comparer.IsBetter(result, best, workArea))
-                    {
+                        best = result;
-                        best = h;
-                        bestScore = scoreH;
-                    }
-                }
-
-                if (v != null && v.Count > 0)
-                {
-                    var scoreV = FillScore.Compute(v, workArea);
-                    context.AngleResults.Add(new AngleResult
-                    {
-                        AngleDeg = angleDeg,
-                        Direction = NestDirection.Vertical,
-                        PartCount = v.Count
-                    });
-
-                    if (best == null || scoreV > bestScore)
-                    {
-                        best = v;
-                        bestScore = scoreV;
-                    }
                 }
 
                 NestEngineBase.ReportProgress(context.Progress, NestPhase.Linear,
                     context.PlateNumber, best, workArea,
-                    $"Linear: {ai + 1}/{angles.Count} angles, {angleDeg:F0}° best = {bestScore.Count} parts");
+                    $"Linear: {ai + 1}/{angles.Count} angles, {angleDeg:F0}° best = {best?.Count ?? 0} parts");
             }
 
             return best ?? new List<Part>();