Orca-Cad: port SnapOrca Design (parametric CAD tab) onto mainline OrcaSlicer

Grafts the sketch-first CAD environment from snaporca-cad onto the mainline
OrcaSlicer/OrcaSlicer base (vs snaporca's Snapmaker/OrcaSlicer base):
- 133 new files: CadDocument/SketchEngine/GeometryEngine/SketchConstraints/
  SketchSolver/SketchInference/ThreadStandards + vendored libslvs solver;
  DesignPanel/DesignCanvas/DesignSketchTool/SketchInlineEditor GUI; GLGizmo
  Primitive/Sketch; 75 design icons; Catch2 tests.
- Integration hooks ported to mainline's diverged versions: Design tab in
  MainFrame, embedded design viewport + sketch overlay + per-canvas chrome
  suppression in GLCanvas3D/PartPlate, gizmo registration, Plater accessors,
  CMake wiring (libslvs subdir, CAD sources, OCCT ModelingAlgorithms=ON).

Structural integration complete; build verification pending.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BVzKmX6Y1aEteit1HTXG4Q

src/slic3r/GUI/PartPlate.hpp

@@ -614,6 +614,11 @@ class PartPlateList : public ObjectBase
     bool render_bedtype_logo = true;
     bool render_plate_settings = true;
     bool render_cali_logo = true;
+    // SnapOrca Design: when true, PartPlate::render skips all overlay chrome
+    // (corner icons, logo watermark, plate numbers) but keeps the bed grid.
+    // Toggled transiently per-frame by GLCanvas3D::_render_platelist for the
+    // DesignCanvas; stays false for the main editor.
+    bool m_hide_chrome = false;
 
     bool m_is_dark = false;
 
@@ -838,6 +843,8 @@ public:
     void render(const Transform3d& view_matrix, const Transform3d& projection_matrix, bool bottom, bool only_current = false, bool only_body = false, int hover_id = -1, bool render_cali = false, bool show_grid = true);
     void set_render_option(bool bedtype_texture, bool plate_settings);
     void set_render_cali(bool value = true) { render_cali_logo = value; }
+    void set_hide_chrome(bool value) { m_hide_chrome = value; }
+    bool get_hide_chrome() const { return m_hide_chrome; }
     void register_raycasters_for_picking(GLCanvas3D& canvas)
     {
         for (auto plate : m_plate_list)