Add null safety in CreateDrawing helper, default Name from class name,
clarify diameter-vs-radius conventions, octagon width definition,
arc direction for rounded rectangles, and MCP parameter mapping.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Defines a parametric shape library with abstract ShapeDefinition base
class and concrete subclasses for common CNC shapes (Tier 1+2).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
