feat: add export_3d_cli tool (kicad-cli, format-dispatched 3D export)

New MCP tool `export_3d_cli` wrapping the kicad-cli 3D subcommands. A
`format` enum {step,glb,stl,ply,brep,xao,vrml} selects the subcommand and
the handler forwards only flags valid for that subcommand: the shared
geometry/include set for step/glb/stl/ply/brep/xao, no-optimize-step for
STEP only, and units + models-dir/models-relative for VRML. Rich CLI
sibling of the existing export_3d / export_vrml (left untouched). Reads
the saved .kicad_pcb.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/tools/registry.ts

@@ -69,6 +69,7 @@ export const toolCategories: ToolCategory[] = [
       "export_pcb_svg",
       "export_pcb_dxf",
       "export_gerber_single",
+      "export_3d_cli",
       "export_pdf",
       "export_svg",
       "export_3d",