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 43 root-level test files into feature-specific subdirectories
mirroring the main codebase structure: Geometry, Fill, BestFit, CutOffs,
CuttingStrategy, Engine, IO. Update namespaces to match folder paths.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
