0.6.7

• New example plate-example-chains.nbcad.jsonc and skill section 5b: construction chains (lines of the printed lengths from the plate edges, holes anchored to their ends) instead of coordinate arithmetic.
• nbcad_run_script returns the engine's feature summary and warnings; new nbcad_check tool compares a feature table with the STEP.
• Both example plates are 12 mm thick so the tapped holes fit.
• Replaces 0.6.6, whose nbcad_check schema did not load.