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.

docs/GAP_ANALYSIS_vs_ONSHAPE.md

@@ -1,10 +1,10 @@
 # SnapOrca-CAD vs Onshape — capability gap analysis
 
 Generated 2026-07-22 by enumerating the source, not from recollection:
-`CadFeatureType` and `add_*` in `src/libslic3r/CadDocument.hpp`, `Tool` in
-`src/slic3r/GUI/DesignPanel.hpp`, `Mode` in `src/slic3r/GUI/DesignSketchTool.hpp`,
-`SketchConstraintType` + `SketchEntity::Type` in `src/libslic3r/SketchEngine.hpp`,
-and the JSON-RPC dispatch in `src/slic3r/GUI/McpControl.cpp`.
+`CadFeatureType` and `add_*` in `src/libslic3r/CAD/CadDocument.hpp`, `Tool` in
+`src/slic3r/GUI/CAD/DesignPanel.hpp`, `Mode` in `src/slic3r/GUI/CAD/DesignSketchTool.hpp`,
+`SketchConstraintType` + `SketchEntity::Type` in `src/libslic3r/CAD/SketchEngine.hpp`,
+and the JSON-RPC dispatch in `src/slic3r/GUI/CAD/McpControl.cpp`.
 
 **Scope note.** Onshape is a cloud PLM platform; SnapOrca is a Design tab inside a
 slicer. A large share of Onshape's surface (release management, branching, real-time

docs/design_tab.md

@@ -320,14 +320,14 @@ Being straight about the edges, so nobody discovers them the hard way:
 
 | Path | Role |
 |---|---|
-| `src/libslic3r/CadDocument.*` | the feature recipe and its replay |
-| `src/libslic3r/GeometryEngine.*` | OCCT wrapper — faces, edges, booleans, healing |
-| `src/libslic3r/SketchEngine.*` | profile → wire → solid |
-| `src/libslic3r/SketchSolver.*` | constraint solving, over the vendored solver |
+| `src/libslic3r/CAD/CadDocument.*` | the feature recipe and its replay |
+| `src/libslic3r/CAD/GeometryEngine.*` | OCCT wrapper — faces, edges, booleans, healing |
+| `src/libslic3r/CAD/SketchEngine.*` | profile → wire → solid |
+| `src/libslic3r/CAD/SketchSolver.*` | constraint solving, over the vendored solver |
 | `src/libslic3r/slvs/` | vendored 2D constraint solver (GPLv3) |
-| `src/slic3r/GUI/DesignPanel.*` | the tab: toolbar, cards, feature tree |
-| `src/slic3r/GUI/DesignCanvas.*` | viewport integration |
-| `src/slic3r/GUI/DesignSketchTool.*` | in-canvas sketching |
+| `src/slic3r/GUI/CAD/DesignPanel.*` | the tab: toolbar, cards, feature tree |
+| `src/slic3r/GUI/CAD/DesignCanvas.*` | viewport integration |
+| `src/slic3r/GUI/CAD/DesignSketchTool.*` | in-canvas sketching |
 
 Build with `-DSLIC3R_CAD=ON` (the default). With it OFF the tab is not compiled and the deps
 prefix matches upstream exactly — see [cad_dependency_weight.md](cad_dependency_weight.md).

docs/design_tab_pr_description.md

@@ -70,4 +70,4 @@ AGPLv3/GPLv3 compatibility argument; this point should be confirmed with upstrea
 
 See the [Where the code lives](docs/design_tab.md#where-the-code-lives) table in the user
 doc for the file-to-role mapping, and [docs/ux/tool_atlas.json](docs/ux/tool_atlas.json) as
-the generated-from source of `src/slic3r/GUI/DesignOffer.hpp`.
+the generated-from source of `src/slic3r/GUI/CAD/DesignOffer.hpp`.

docs/ux/mockups/gen_offer_table.py

@@ -7,7 +7,7 @@ The map exists ONCE. The mockups and the shipping menu read the same rows in the
 order from the same file, so a drawing and the product cannot drift apart — which is the
 only way row constancy (charter 4.1) survives contact with a codebase.
 
-Output: src/slic3r/GUI/DesignOffer.hpp, checked in and never hand-edited.
+Output: src/slic3r/GUI/CAD/DesignOffer.hpp, checked in and never hand-edited.
 """
 
 import json
@@ -17,7 +17,7 @@ HERE = os.path.dirname(os.path.abspath(__file__))
 UX = os.path.dirname(HERE)
 REPO = os.path.dirname(os.path.dirname(UX))
 ATLAS = os.path.join(UX, "tool_atlas.json")
-OUT = os.path.join(REPO, "src", "slic3r", "GUI", "DesignOffer.hpp")
+OUT = os.path.join(REPO, "src", "slic3r", "GUI", "CAD", "DesignOffer.hpp")
 
 # selection id -> C++ enumerator
 ENUM = {

docs/ux/tool_atlas.json

@@ -3,11 +3,11 @@
     "Source of truth for the object-driven tool offer (see docs/cad_ux_guidelines.md 4.1).",
     "Every verb, the selections it accepts, the document state it needs, and its fixed",
     "compass address. Extracted from the code, not from memory:",
-    "  verbs + shortcuts + refusal messages -> src/slic3r/GUI/DesignPanel.cpp (feat_dropdown",
+    "  verbs + shortcuts + refusal messages -> src/slic3r/GUI/CAD/DesignPanel.cpp (feat_dropdown",
     "    call sites at 524/662/734/790/874/904, sk_key table at 369-400, m_keys_feature)",
-    "  kernel coverage            -> src/libslic3r/CadDocument.hpp  (enum CadFeatureType)",
-    "  headless coverage          -> src/slic3r/GUI/McpControl.cpp  (method == \"...\")",
-    "  selection kinds            -> src/slic3r/GUI/DesignCanvas.hpp (the on_*_selected callbacks)",
+    "  kernel coverage            -> src/libslic3r/CAD/CadDocument.hpp  (enum CadFeatureType)",
+    "  headless coverage          -> src/slic3r/GUI/CAD/McpControl.cpp  (method == \"...\")",
+    "  selection kinds            -> src/slic3r/GUI/CAD/DesignCanvas.hpp (the on_*_selected callbacks)",
     "gen_offer_mockups.py reads this file; the eventual C++ offer table is generated from it",
     "too, so the map exists once."
   ],