build123d MCP

Gives Claude direct access to build123d's CAD operations so it can build, inspect, and iterate on 3D geometry instead of writing blind scripts. Execute code in a persistent session, render views as PNG or SVG, measure volume and clearance, export to STEP or STL, and load parts from bd_warehouse's fastener catalog. The workflow model is smart: use execute() for simple shapes, but for complex geometry with high face counts or threading, probe the API through the MCP then build in a standalone Python script and import the result to verify. Includes AST sandboxing and a restricted builtins layer so you can point it at LLM-generated code without immediately regretting it.