v0.9.0 — structural FEM (M13)

4 new tools on top of FreeCAD's bundled CalculiX + Gmsh: setup_analysis (material table or E/nu/density/yield, fixed faces, force/pressure/self-weight, 2nd-order Gmsh mesh), run_analysis (max von Mises + location, max displacement, safety factor, verdict, stress colormap in the 3D view), inspect_results (top nodes, per-face maxima, field switch), suggest_reinforcement (thicken/fillet/rib/material/load candidates, never auto-applied). Plus check_printability(paint=True) face coloring and get_mass_properties(stability=True) footprint/tip-over. 35 tools, 256 headless tests. Cantilever benchmark within 2 % of theory.