Predispose the Design tab to run under an external MCP agent. New
McpControl.{cpp,hpp} embeds a line-delimited JSON-RPC 2.0 server over a
Unix domain socket, off unless env SNAPORCA_MCP is set. Requests are
marshalled onto the wx main thread and run through the SAME CadDocument
kernel the GUI uses, via two thin DesignPanel hooks (mcp_doc /
mcp_after_change) — no parallel engine.
Slice-1 methods: describe_tools (introspection -> the bridge builds tool
schemas), describe_scene (feature tree + per-body bounding boxes), and
extrude (centred rectangle sketch -> new solid). Every op returns its
full post-state. POSIX-only; Windows compiles to a no-op.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BVzKmX6Y1aEteit1HTXG4Q
