fix(cnc): keep hole sub-programs private to each program copy

Program.Clone deep-copied the SubPrograms dictionary but left every
SubProgramCall pointing at the source's sub-program, and
SubProgramCall.Clone went through the Rotation setter, which re-rotated
that shared program to the call's stale angle. Copying a program with
hole lead-ins therefore rotated the source's holes, and rotating the
copy rotated the source again.

Program.Rotate also rotated a shared sub-program once per call, so two
identical holes (one deduplicated sub-program) turned twice.

Clone now binds calls to one private copy per shared sub-program
without re-aligning it, and Rotate turns each distinct sub-program once.

OpenNest.Core/CNC/SubProgramCall.cs

@@ -79,12 +79,28 @@ namespace OpenNest.CNC
         }
 
         /// <summary>
-        /// Gets a shallow copy.
+        /// Gets a shallow copy that references the same program. Copies the fields
+        /// directly: going through the setters would re-align (rotate) the shared program.
         /// </summary>
         /// <returns></returns>
         public ICode Clone()
         {
-            return new SubProgramCall(program, Rotation) { Id = Id, Offset = Offset };
+            return new SubProgramCall
+            {
+                program = program,
+                rotation = rotation,
+                Id = Id,
+                Offset = Offset,
+            };
+        }
+
+        /// <summary>
+        /// Points the call at <paramref name="copy"/>, a copy of its current program, without
+        /// re-aligning its rotation: the copy already has the geometry the call executes.
+        /// </summary>
+        internal void BindProgram(Program copy)
+        {
+            program = copy;
         }
 
         public override string ToString()