Design: port the Orca-widget rebuild and the mouse-press fix from snaporca

Mirrors snaporca-cad a016dffb48 + 4b828c4798 so the two forks do not drift:

- Sidebar on Orca's widget set: ComboBox for all 25 pickers, StaticBox
  frames for the tool cards / feature tree / bodies list, framed double
  spins, and no stack of full-width action buttons (Prepare's left panel
  is parameters only).
- Toolbar: document group + undo/redo + mode-gated tools, commit far
  right, ordered via keyed slots, at Prepare's 40 px / 4 px geometry.
- Polygon options and a new Move/Rotate card (distance, axis, angle) in
  the sidebar instead of inline in the toolbar row.
- DesignSketchTool: stop consuming the LeftDown over a solid. Orca starts
  a rotate drag on the press, so swallowing it killed orbit/pan whenever a
  body was on screen. The pick now resolves on LeftUp within 4 px.

DesignSketchTool.{cpp,hpp} were byte-identical across the forks and are
copied verbatim. DesignPanel.cpp needed one hand-merge: mainline's
DropDown is Item-based (DropDown::Item{text,tip,icon}, DropDown(items&))
where snaporca passes parallel vectors, so feat_dropdown/ToolFlyout keep
the mainline form. Checked field-by-field against this fork's
Widgets/DropDown.hpp.

scripts/docker-iter-build.sh: mount the root CMakeLists.txt and cmake/
rather than inheriting the baked copies, which silently drops the
SLIC3R_CAD gate, and stop defaulting to snaporca's build volume - sharing
it made the two forks overwrite each other's cache and binary.

NOT COMPILED. This fork needs Eigen 5.0.1 (find_package(Eigen3 5.0.1
REQUIRED)) while the available snaporca-deps image supplies 3.3, so it
needs its own deps build to verify. The behaviour above was verified only
on the snaporca side.

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

src/slic3r/GUI/DesignSketchTool.hpp

@@ -96,6 +96,11 @@ public:
     struct DisplaySketch { std::vector<SketchEntity> entities; SketchPlane plane; int feature{-1}; };
     void set_display_sketches(std::vector<DisplaySketch> ds) { m_display_sketches = std::move(ds); }
     void set_highlight_sketches(std::vector<std::pair<int, ColorRGBA>> hl) { m_hl_sketches = std::move(hl); }
+    // Solid pick is resolved on LeftUp (see on_mouse): consuming the press broke orbit/pan.
+    int  m_pick_press_x = 0;
+    int  m_pick_press_y = 0;
+    bool m_pick_pending = false;
+
     bool has_display() const { return m_active || !m_display_sketches.empty()
                                       || (m_solid_bodies != nullptr && !m_solid_bodies->empty())
                                       || !m_datum_planes.empty()