fix: ensure absolute coordinates and .lib extension in post output

Convert programs to absolute mode before extracting features for
Cincinnati post output, fixing incorrect coordinates when programs
are stored in incremental mode. Also ensure G89 library names
always end with .lib extension.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

OpenNest.Posts.Cincinnati/CincinnatiPartSubprogramWriter.cs

@@ -99,6 +99,7 @@ public sealed class CincinnatiPartSubprogramWriter
                     mapping[key] = subNum;
 
                     var pgm = part.Program.Clone() as Program;
+                    pgm.Mode = Mode.Absolute;
                     var bbox = pgm.BoundingBox();
                     pgm.Offset(-bbox.Location.X, -bbox.Location.Y);