Design tab: translatable offer, one vocabulary, reports in the status line

- Offer table: user-facing strings carry the L() marker so xgettext
  extracts them; DesignOffer.hpp, DesignSketchTool.cpp and
  SketchInlineEditor.cpp are listed in localization/i18n/list.txt.
- Offer: model-mode Constrain sits in the same row as the sketch one;
  Interference is wired; Rib shows its R key; a verb that accepts the
  selection but is blocked by the document stays greyed with its reason
  instead of vanishing from the submenu; one refusal wording per verb.
- Extrude infers Join when the profile touches a solid (new
  CadDocument::body_touching_sketch) and on face push/pull; New body in
  free space. Revolve/Sweep/Loft/Boolean use the same result words.
- Interference and volume/area reports go to the status line in mm3/mm2
  instead of modal dialogs; Delete Body no longer asks (it is undoable).
- New feature names match the card header ("Extrude 3"), translated;
  "Coordinate system", "Angle (°)", center/color spelling, translated
  face and length readouts, slot hints say width.
- CAD gizmos in Prepare are selectable only with the CAD feature on; the
  sketch auto-close setting is stored per design.
- Docs: confirm/cancel rules, enabling the feature and MCP in
  design_tab.md; drift-only right-click in interaction-model.md; the
  portability note rewritten to describe the integration as it is.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QK4VgguuCAk2hZLWgcjJb9

src/slic3r/GUI/Preferences.cpp

@@ -9,7 +9,6 @@
 #include "I18N.hpp"
 #include "libslic3r/AppConfig.hpp"
 #include "libslic3r/Format/DRC.hpp"
-#include "libslic3r/CAD/SketchEngine.hpp"
 #include <wx/language.h>
 #include "OG_CustomCtrl.hpp"
 #include "wx/graphics.h"
@@ -1765,13 +1764,6 @@ void PreferencesDialog::create_items()
            "parametrically. This feature is experimental and still under development."),
         "enable_cad_feature", _L("(Requires restart)"));
     g_sizer->Add(item_cad_feature);
-
-    auto item_auto_close_sketch_loops = create_item_checkbox(_L("Auto-close sketch loops"),
-        _L("Treat sketch endpoints within 0.001 mm as one joint and weld the loop shut. "
-           "Off: only exactly coincident endpoints join, so a loop with a tiny gap is "
-           "shown as open instead of being closed for you."),
-        "auto_close_sketch_loops");
-    g_sizer->Add(item_auto_close_sketch_loops);
 #endif
 
 #if 0
@@ -1861,11 +1853,18 @@ void PreferencesDialog::create_items()
                "disc with a roll quadrant. A face's orientation is read without being learned. "
                "Turn this off for the conventional CAD representation."), "design_connector_face_glyph");
         g_sizer->Add(item_connector_face_glyph);
-    }
 
-    // Push the weld preference into the kernel now so toggling it takes effect without
-    // a restart (the sketch tool also re-pushes on activation, see DesignSketchTool::begin).
-    Slic3r::set_sketch_auto_close(wxGetApp().is_auto_close_sketch_loops());
+        // Saved WITH each design (it decides which loops are closed, i.e. what solid a project
+        // rebuilds into), so it applies to designs started from now on; an open design keeps
+        // the rule it was made with.
+        auto item_auto_close_sketch_loops = create_item_checkbox(_L("Auto-close sketch loops"),
+            _L("Treat sketch endpoints within 0.001 mm as one joint and weld the loop shut. "
+               "Off: only exactly coincident endpoints join, so a loop with a tiny gap is "
+               "shown as open instead of being closed for you. Saved with each design; "
+               "applies to designs started after the change."),
+            "auto_close_sketch_loops");
+        g_sizer->Add(item_auto_close_sketch_loops);
+    }
 #endif
 
     std::vector<wxString> ButtonDragActions = {_L("None"), _L("Pan"), _L("Rotate")};