ProgramReader now supports G-code user variables with a two-pass
approach: first pass collects variable definitions (name = expression
[inline] [global]) and evaluates them via topological sort and
ExpressionEvaluator; second pass parses G-code lines with $name
substitution and VariableRef tracking on motion and feedrate objects.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Move DxfImporter, DxfExporter, NestReader, NestWriter, ProgramReader,
and Extensions into a new OpenNest.IO class library. The WinForms project
now references OpenNest.IO instead of ACadSharp directly.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
