Replaces the .nstdot nest-template mechanism for new-nest plate defaults. NestDefaults persists units, plate size, quadrant, part spacing, and edge spacing to a single JSON file (DefaultPath: %APPDATA%/OpenNest/defaults.json). Load never throws: a missing, corrupt, or partially valid file degrades field-by-field to the built-in fallback values, and unknown fields or a future version number are ignored.