Design: slot Radius caption, keyboard offer, plane combo removal, mass props, docs

Mirror of snaporca ac85277bac..0e7cb3ec78 (six changes, applied as a patch to
DesignPanel.cpp rather than copied, so this fork's 30 permitted divergent lines survive
— parity re-checked afterwards: the five shared files are byte-identical, DesignCanvas.cpp
and DesignPanel.cpp differ by exactly 16 and 30 lines).

- The straight slot's inline field says Radius, which is what it sets. It stores the
  half-width and passed the typed number through unchanged, so 30 produced a 60 mm slot.
- The offer opens from the keyboard (Menu, Shift+F10), anchored on the viewport rather
  than wherever the pointer happens to be. The card hint names the new route.
- The sketch card's Plane combo is gone; the plane comes from the viewport. Also stops
  build_candidate collapsing a face plane to a base plane while editing.
- Mass properties and the dead Edit row are wired into the offer; DesignOffer.hpp is
  regenerated from tool_atlas.json, verified by re-running the generator and diffing.
- docs/rig_build_traps.md + scripts/rig-build.sh, which derives its fork identity from
  project() so it cannot be pointed at the other fork's image or volume.
- docs/design_tab.md refreshed (44 commits stale) + a PR description, with this fork's
  own merge-base and diff shape rather than snaporca's.

Built green in the deps container with the new script and verified on the rig: Menu and
Shift+F10 both open the offer at the viewport centre with the pointer parked off-canvas,
and the sketch card shows no Plane row.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LyRwbuq6fjn3VV9U9UvhBM

src/slic3r/GUI/DesignSketchTool.cpp

@@ -1256,7 +1256,7 @@ void DesignSketchTool::open_primary_autoedit()
         const double Lc = d.norm();
         double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
         m_autoedit_dims.push_back({ m_live_slot_len_label, Lc, [this, fi](double v){ const Feature& g = m_features[fi]; set_slot(fi, v, g.param); }, span(fi), "Length" });
-        m_autoedit_dims.push_back({ m_live_slot_w_label, f.param, [this, fi](double v){ const Feature& g = m_features[fi]; set_slot(fi, (g.c1-g.c0).norm(), std::max(1e-3, v)); }, span(fi), "Width" });
+        m_autoedit_dims.push_back({ m_live_slot_w_label, f.param, [this, fi](double v){ const Feature& g = m_features[fi]; set_slot(fi, (g.c1-g.c0).norm(), std::max(1e-3, v)); }, span(fi), "Radius" });
         m_autoedit_dims.push_back({ m_live_slot_angle_label, deg, [this, fi](double v){ set_slot_angle(fi, v); }, span(fi), "Angle" });
     }
     if (m_live_arc_ei >= 0) {   // arc Radius is already a scalar step above; add its sweep angle
@@ -1838,7 +1838,7 @@ void DesignSketchTool::open_slot_editor(int fi, int which)
     double deg = std::atan2(d.y(), d.x()) * 180.0 / M_PI; if (deg < 0.0) deg += 360.0;
     const double v = (which == 0) ? d.norm() : (which == 1) ? f.param : deg;
     const wxPoint px(m_last_mouse_x, m_last_mouse_y);
-    on_inline_edit(px, v, which == 0 ? "Length" : which == 1 ? "Width" : "Angle",
+    on_inline_edit(px, v, which == 0 ? "Length" : which == 1 ? "Radius" : "Angle",
         [this, fi, which](double nv) {
             const Feature& g = m_features[fi];
             if      (which == 0) set_slot(fi, nv, g.param);