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.Core/CutParameters.cs

@@ -11,11 +11,12 @@ public class CutParameters
     public string PostProcessor { get; set; }
     public Units Units { get; set; }
 
-    public static CutParameters Default => new()
-    {
-        Feedrate = 100,
-        RapidTravelRate = 300,
-        PierceTime = TimeSpan.FromSeconds(0.5),
-        Units = OpenNest.Units.Inches
-    };
+    public static CutParameters Default =>
+        new()
+        {
+            Feedrate = 100,
+            RapidTravelRate = 300,
+            PierceTime = TimeSpan.FromSeconds(0.5),
+            Units = OpenNest.Units.Inches,
+        };
 }