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/CNC/SubProgramCall.cs

@@ -9,9 +9,7 @@ namespace OpenNest.CNC
         private double rotation;
         private Program program;
 
-        public SubProgramCall()
-        {
-        }
+        public SubProgramCall() { }
 
         public SubProgramCall(Program program, double rotation)
         {