Design tab: move the CAD sources into their own folder

Review request on PR #15238: "Place CAD-related files (e.g. CadDocument/
GeometryEngine) into a separate folder."

  src/libslic3r/CAD/     the kernel — CadDocument, GeometryEngine, the four
                         Sketch* units, SketchSolver, ThreadStandards
  src/slic3r/GUI/CAD/    the tab — DesignPanel, DesignCanvas, DesignSketchTool,
                         SketchInlineEditor, McpControl, generated DesignOffer

Pure relocation: no line of logic changes. Two include rewrites follow from it —
files that moved re-spell their own neighbours against src/ (already on the
include path), and files that did not move pick up the new folder. docs and
docs/ux/mockups/gen_offer_table.py follow the same paths.

Verified: libslic3r, libslic3r_gui and libslic3r_tests all build, CAD suite green
at 2518 assertions in 194 test cases, and the sibling fork builds identically —
17 shared sources still byte-identical, 8 diverging by their expected counts.

src/libslic3r/CAD/CadDocument.cpp

@@ -1,7 +1,7 @@
-#include "CadDocument.hpp"
-#include "SketchConstraints.hpp"
-#include "SketchSolver.hpp"
-#include "SketchImport.hpp"   // transform_regions for imported art
+#include "libslic3r/CAD/CadDocument.hpp"
+#include "libslic3r/CAD/SketchConstraints.hpp"
+#include "libslic3r/CAD/SketchSolver.hpp"
+#include "libslic3r/CAD/SketchImport.hpp"   // transform_regions for imported art
 
 #include <array>
 

src/libslic3r/CAD/CadDocument.hpp

@@ -1,10 +1,10 @@
 #ifndef slic3r_CadDocument_hpp_
 #define slic3r_CadDocument_hpp_
 
-#include "TriangleMesh.hpp"
-#include "SketchEngine.hpp"
-#include "GeometryEngine.hpp"   // FaceGroup
-#include "Color.hpp"            // ColorRGBA (per-body display colour override)
+#include "libslic3r/TriangleMesh.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"   // FaceGroup
+#include "libslic3r/Color.hpp"            // ColorRGBA (per-body display colour override)
 
 #include <TopoDS_Shape.hxx>
 #include <TopoDS_Wire.hxx>

src/libslic3r/CAD/GeometryEngine.cpp

@@ -1,4 +1,4 @@
-#include "GeometryEngine.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
 
 #include <BRepMesh_IncrementalMesh.hxx>
 #include <BRep_Tool.hxx>

src/libslic3r/CAD/GeometryEngine.hpp

@@ -1,7 +1,7 @@
 #ifndef slic3r_GeometryEngine_hpp_
 #define slic3r_GeometryEngine_hpp_
 
-#include "TriangleMesh.hpp"
+#include "libslic3r/TriangleMesh.hpp"
 
 #include <BRepPrimAPI_MakeBox.hxx>
 #include <BRepPrimAPI_MakeCylinder.hxx>

src/libslic3r/CAD/SketchConstraints.cpp

@@ -1,4 +1,4 @@
-#include "SketchConstraints.hpp"
+#include "libslic3r/CAD/SketchConstraints.hpp"
 #include <Eigen/Dense>
 #include <cmath>
 

src/libslic3r/CAD/SketchEngine.cpp

@@ -1,4 +1,4 @@
-#include "SketchEngine.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
 
 #include <algorithm>
 #include <cmath>

src/libslic3r/CAD/SketchEngine.hpp

@@ -1,9 +1,9 @@
 #ifndef slic3r_SketchEngine_hpp_
 #define slic3r_SketchEngine_hpp_
 
-#include "TriangleMesh.hpp"
+#include "libslic3r/TriangleMesh.hpp"
 #include "libslic3r/Point.hpp"
-#include "GeometryEngine.hpp"
+#include "libslic3r/CAD/GeometryEngine.hpp"
 
 #include <gp_Pln.hxx>
 #include <gp_Ax3.hxx>

src/libslic3r/CAD/SketchImport.cpp

@@ -1,11 +1,11 @@
-#include "SketchImport.hpp"
+#include "libslic3r/CAD/SketchImport.hpp"
 
-#include "Emboss.hpp"
-#include "NSVGUtils.hpp"
-#include "ExPolygon.hpp"
-#include "TextConfiguration.hpp"   // FontProp
-#include "libslic3r.h"             // SCALING_FACTOR
-#include "Utils.hpp"               // resources_dir
+#include "libslic3r/Emboss.hpp"
+#include "libslic3r/NSVGUtils.hpp"
+#include "libslic3r/ExPolygon.hpp"
+#include "libslic3r/TextConfiguration.hpp"   // FontProp
+#include "libslic3r/libslic3r.h"             // SCALING_FACTOR
+#include "libslic3r/Utils.hpp"               // resources_dir
 
 #include <algorithm>
 #include <limits>

src/libslic3r/CAD/SketchImport.hpp

@@ -1,7 +1,7 @@
 #ifndef slic3r_SketchImport_hpp_
 #define slic3r_SketchImport_hpp_
 
-#include "Point.hpp"   // Vec2d
+#include "libslic3r/Point.hpp"   // Vec2d
 
 #include <string>
 #include <vector>

src/libslic3r/CAD/SketchInference.cpp

@@ -1,4 +1,4 @@
-#include "SketchInference.hpp"
+#include "libslic3r/CAD/SketchInference.hpp"
 
 #include <cmath>
 

src/libslic3r/CAD/SketchInference.hpp

@@ -1,7 +1,7 @@
 #ifndef slic3r_SketchInference_hpp_
 #define slic3r_SketchInference_hpp_
 
-#include "SketchEngine.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
 #include <vector>
 #include <optional>
 #include <cmath>

src/libslic3r/CAD/SketchSolver.cpp

@@ -1,4 +1,4 @@
-#include "SketchSolver.hpp"
+#include "libslic3r/CAD/SketchSolver.hpp"
 
 #include <slvs.h>
 

src/libslic3r/CAD/SketchSolver.hpp

@@ -6,7 +6,7 @@
 // hand-rolled SketchConstraints: full constraint set, real DoF counting, and
 // over-constrained (bad-constraint) detection. Solves on a fixed 2D XY workplane.
 
-#include "SketchEngine.hpp"
+#include "libslic3r/CAD/SketchEngine.hpp"
 #include <vector>
 
 namespace Slic3r {

src/libslic3r/CAD/ThreadStandards.cpp

@@ -1,4 +1,4 @@
-#include "ThreadStandards.hpp"
+#include "libslic3r/CAD/ThreadStandards.hpp"
 
 namespace Slic3r {
 

src/libslic3r/CMakeLists.txt

@@ -489,22 +489,22 @@ set(lisbslic3r_sources
 # vendored SolveSpace solver; both are pulled in only when SLIC3R_CAD is ON.
 if (SLIC3R_CAD)
     list(APPEND lisbslic3r_sources
-            GeometryEngine.cpp
-            GeometryEngine.hpp
-            SketchEngine.cpp
-            SketchEngine.hpp
-            SketchConstraints.cpp
-            SketchConstraints.hpp
-            SketchSolver.cpp
-            SketchSolver.hpp
-            SketchInference.cpp
-            SketchInference.hpp
-            SketchImport.cpp
-            SketchImport.hpp
-            CadDocument.cpp
-            CadDocument.hpp
-            ThreadStandards.cpp
-            ThreadStandards.hpp
+            CAD/GeometryEngine.cpp
+            CAD/GeometryEngine.hpp
+            CAD/SketchEngine.cpp
+            CAD/SketchEngine.hpp
+            CAD/SketchConstraints.cpp
+            CAD/SketchConstraints.hpp
+            CAD/SketchSolver.cpp
+            CAD/SketchSolver.hpp
+            CAD/SketchInference.cpp
+            CAD/SketchInference.hpp
+            CAD/SketchImport.cpp
+            CAD/SketchImport.hpp
+            CAD/CadDocument.cpp
+            CAD/CadDocument.hpp
+            CAD/ThreadStandards.cpp
+            CAD/ThreadStandards.hpp
         )
 endif ()