style: apply CSharpier formatting to all C# sources

Repo-wide sweep with the pinned CSharpier 1.3.0 tool. Whitespace and
line-wrapping only; OpenNest.Engine.Tests (109) and OpenNest.IO.Tests
pass after reformat, full solution builds 0 errors.

Added .csharpierignore so csproj/config XML keeps its existing layout
(CSharpier's XML wrapping churns attributes with zero benefit).

Formatting is now enforceable: dotnet csharpier check . passes.

OpenNest.Engine/Fill/ShrinkFiller.cs

@@ -1,13 +1,17 @@
-using OpenNest.Geometry;
-using OpenNest.RectanglePacking;
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
+using OpenNest.Geometry;
+using OpenNest.RectanglePacking;
 
 namespace OpenNest.Engine.Fill
 {
-    public enum ShrinkAxis { Width, Length }
+    public enum ShrinkAxis
+    {
+        Width,
+        Length,
+    }
 
     public class ShrinkResult
     {
@@ -23,14 +27,16 @@ namespace OpenNest.Engine.Fill
     {
         public static ShrinkResult Shrink(
             Func<NestItem, Box, List<Part>> fillFunc,
-            NestItem item, Box box,
+            NestItem item,
+            Box box,
             double spacing,
             ShrinkAxis axis,
             CancellationToken token = default,
             int targetCount = 0,
             IProgress<NestProgress> progress = null,
             int plateNumber = 0,
-            List<Part> placedParts = null)
+            List<Part> placedParts = null
+        )
         {
             var startBox = box;
             if (targetCount > 0)
@@ -38,8 +44,7 @@ namespace OpenNest.Engine.Fill
 
             var parts = fillFunc(item, startBox);
 
-            if (targetCount > 0 && startBox != box
-                && (parts == null || parts.Count < targetCount))
+            if (targetCount > 0 && startBox != box && (parts == null || parts.Count < targetCount))
             {
                 parts = fillFunc(item, box);
             }
@@ -47,9 +52,8 @@ namespace OpenNest.Engine.Fill
             if (parts == null || parts.Count == 0)
                 return new ShrinkResult { Parts = parts ?? new List<Part>(), Dimension = 0 };
 
-            var shrinkTarget = targetCount > 0
-                ? System.Math.Min(targetCount, parts.Count)
-                : parts.Count;
+            var shrinkTarget =
+                targetCount > 0 ? System.Math.Min(targetCount, parts.Count) : parts.Count;
 
             if (parts.Count > shrinkTarget)
                 parts = TrimToCount(parts, shrinkTarget, axis);
@@ -62,16 +66,22 @@ namespace OpenNest.Engine.Fill
         }
 
         private static void ReportShrinkProgress(
-            IProgress<NestProgress> progress, int plateNumber,
-            List<Part> placedParts, List<Part> bestParts,
-            Box workArea, ShrinkAxis axis, double dim)
+            IProgress<NestProgress> progress,
+            int plateNumber,
+            List<Part> placedParts,
+            List<Part> bestParts,
+            Box workArea,
+            ShrinkAxis axis,
+            double dim
+        )
         {
             if (progress == null)
                 return;
 
-            var allParts = placedParts != null && placedParts.Count > 0
-                ? new List<Part>(placedParts.Count + bestParts.Count)
-                : new List<Part>(bestParts.Count);
+            var allParts =
+                placedParts != null && placedParts.Count > 0
+                    ? new List<Part>(placedParts.Count + bestParts.Count)
+                    : new List<Part>(bestParts.Count);
 
             if (placedParts != null && placedParts.Count > 0)
                 allParts.AddRange(placedParts);
@@ -79,14 +89,17 @@ namespace OpenNest.Engine.Fill
 
             var desc = $"Shrink {axis}: {bestParts.Count} parts, dim={dim:F1}";
 
-            NestEngineBase.ReportProgress(progress, new ProgressReport
-            {
-                Phase = NestPhase.Custom,
-                PlateNumber = plateNumber,
-                Parts = allParts,
-                WorkArea = workArea,
-                Description = desc,
-            });
+            NestEngineBase.ReportProgress(
+                progress,
+                new ProgressReport
+                {
+                    Phase = NestPhase.Custom,
+                    PlateNumber = plateNumber,
+                    Parts = allParts,
+                    WorkArea = workArea,
+                    Description = desc,
+                }
+            );
         }
 
         /// <summary>
@@ -94,8 +107,14 @@ namespace OpenNest.Engine.Fill
         /// that fits roughly the target count. Scales the shrink axis proportionally
         /// from the full-area count down to the target, with margin.
         /// </summary>
-        internal static Box EstimateStartBox(NestItem item, Box box,
-            double spacing, ShrinkAxis axis, int targetCount, double marginFactor = 1.3)
+        internal static Box EstimateStartBox(
+            NestItem item,
+            Box box,
+            double spacing,
+            ShrinkAxis axis,
+            int targetCount,
+            double marginFactor = 1.3
+        )
         {
             var bbox = item.Drawing.Program.BoundingBox();
             if (bbox.Width <= 0 || bbox.Length <= 0)
@@ -105,7 +124,10 @@ namespace OpenNest.Engine.Fill
 
             // Use FillBestFit for a fast, accurate rectangle count on the full box.
             var bin = new Bin { Size = new Size(box.Width, box.Length) };
-            var packItem = new Item { Size = new Size(bbox.Width + spacing, bbox.Length + spacing) };
+            var packItem = new Item
+            {
+                Size = new Size(bbox.Width + spacing, bbox.Length + spacing),
+            };
             var packer = new FillBestFit(bin);
             packer.Fill(packItem);
             var fullCount = bin.Items.Count;
@@ -130,9 +152,7 @@ namespace OpenNest.Engine.Fill
         {
             var placedBox = parts.Cast<IBoundable>().GetBoundingBox();
 
-            return axis == ShrinkAxis.Width
-                ? placedBox.Right - box.X
-                : placedBox.Top - box.Y;
+            return axis == ShrinkAxis.Width ? placedBox.Right - box.X : placedBox.Top - box.Y;
         }
 
         /// <summary>