Consolidate duplicated static methods (SplitFeatures, ComputeCutDistance,
IsFeatureEtch, feature ordering) from CincinnatiSheetWriter and
CincinnatiPartSubprogramWriter into a shared FeatureUtils class. Move
inline sub-program registry building from Post() into
CincinnatiPartSubprogramWriter.BuildRegistry().
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
