CAD kernel: fix the sketch solver, trim/offset/mirror, and history references

Sketch layer
- Trim/extend of an arc (and a circle opened into an arc) rewrites p0/p1 from the new angles;
  the wire builder, the solver and snapping read them.
- Tangency binds the arc end that touches the line (or the other arc) instead of always the
  start, so a fillet tangent to both legs solves; circle-circle / circle-arc tangency uses the
  centre distance instead of CURVE_CURVE_TANGENT, which aborts on a circle.
- Point-on-line distances and circle-line tangency keep the side the geometry is on; a point
  on an arc's rim uses PT_ON_CIRCLE.
- The partitioned solve keeps constraints onto the origin/axes and counts free entities' DOF.
- Zero-radius circles get no solver primitive and build no wire; constraints the solver cannot
  apply are reported in SketchSolveResult::skipped.
- EllipseArc: mirror no longer yields the complement; after a solve its angles and ends are
  re-derived; on the XZ plane it is no longer built mirrored.
- Offset: a circle follows the "+d = left of travel" rule (it shrinks, like a CCW arc chain);
  chains are joined at the weld tolerance. Bridge end pole fixed (G1, no cusp). Negative-scale
  transforms keep arcs and ellipses on their ends. Inference tolerances aligned with the weld.

Model layer
- Body references follow the body across delete / reorder / hide (resolved by the feature
  that made it); datum-plane ordinals are re-pointed; an index past the end is an error, not
  "the last body". New set_feature_enabled(). A move that puts a consumer above its input is
  refused.
- Threads made from now on read thread_radius as the nominal major radius (internal: bore to
  minor, groove to major; external: groove cut into the rod); older recipes build as before.
  Bad thread parameters say why. Circular patterns span their angle end to end (new ones);
  add_pattern pivots on the modeling origin.
- clear() drops variables; expression fields the GUI offers are bindable (thread_diameter,
  helix_*, thicken_thickness, ...); deg()/rad() in expressions; the recipe saves the modeling
  origin and body colours; names/colours follow bodies by identity.
- Boolean and dress-up failures throw instead of returning the input; one produces_body();
  hole standards corrected (82° inch countersinks, UNC names, #10-24); legacy profile solve
  validates indices and writes back only on success; v4 recipes read with a frozen field list.

Tests cover each of the above.

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

src/libslic3r/CAD/GeometryEngine.cpp

@@ -275,21 +275,21 @@ FaceGroup GeometryEngine::classify_face(const TopoDS_Face& face, const TopoDS_Sh
 
 std::vector<TopoDS_Edge> GeometryEngine::collect_edges(const TopoDS_Shape& solid, FaceGroup target)
 {
+    // Each edge ONCE. An explorer visits a shared edge from both of its faces, so walking one
+    // handed every edge to the fillet twice; the de-duplicated map is also what edge_by_index
+    // numbers edges by.
     std::vector<TopoDS_Edge> result;
+    TopTools_IndexedDataMapOfShapeListOfShape edgeFaceMap;
+    TopExp::MapShapesAndAncestors(solid, TopAbs_EDGE, TopAbs_FACE, edgeFaceMap);
     if (target == FaceGroup::All) {
-        for (TopExp_Explorer exp(solid, TopAbs_EDGE); exp.More(); exp.Next())
-            result.push_back(TopoDS::Edge(exp.Current()));
+        for (int i = 1; i <= edgeFaceMap.Extent(); ++i)
+            result.push_back(TopoDS::Edge(edgeFaceMap.FindKey(i)));
         return result;
     }
 
-    // Build edge-to-face map once
-    TopTools_IndexedDataMapOfShapeListOfShape edgeFaceMap;
-    TopExp::MapShapesAndAncestors(solid, TopAbs_EDGE, TopAbs_FACE, edgeFaceMap);
-
-    for (TopExp_Explorer edgeExp(solid, TopAbs_EDGE); edgeExp.More(); edgeExp.Next()) {
-        const TopoDS_Edge& edge = TopoDS::Edge(edgeExp.Current());
-        if (!edgeFaceMap.Contains(edge)) continue;
-        const TopTools_ListOfShape& faces = edgeFaceMap.FindFromKey(edge);
+    for (int ei = 1; ei <= edgeFaceMap.Extent(); ++ei) {
+        const TopoDS_Edge& edge = TopoDS::Edge(edgeFaceMap.FindKey(ei));
+        const TopTools_ListOfShape& faces = edgeFaceMap.FindFromIndex(ei);
 
         bool include = false;
         for (auto it = faces.begin(); it != faces.end(); ++it) {
@@ -325,12 +325,14 @@ std::vector<TopoDS_Edge> GeometryEngine::collect_edges(const TopoDS_Shape& solid
 
 // ---- Fillet/Chamfer ----
 
+// All four dress-up entry points fail the same way — with a reason — instead of two of them
+// handing the solid back unchanged, which recompute then reported as a success.
 TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radius, FaceGroup faces)
 {
-    if (radius <= 0.001) return solid;
+    if (radius <= 0.001) throw std::runtime_error("the fillet radius must be greater than 0");
 
     std::vector<TopoDS_Edge> edges = collect_edges(solid, faces);
-    if (edges.empty()) return solid;
+    if (edges.empty()) throw std::runtime_error("no edges to fillet in that group");
 
     BRepFilletAPI_MakeFillet fillet(solid);
     for (const auto& edge : edges)
@@ -346,10 +348,10 @@ TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radi
 
 TopoDS_Shape GeometryEngine::apply_chamfer(const TopoDS_Shape& solid, double distance, FaceGroup faces)
 {
-    if (distance <= 0.001) return solid;
+    if (distance <= 0.001) throw std::runtime_error("the chamfer distance must be greater than 0");
 
     std::vector<TopoDS_Edge> edges = collect_edges(solid, faces);
-    if (edges.empty()) return solid;
+    if (edges.empty()) throw std::runtime_error("no edges to chamfer in that group");
 
     BRepFilletAPI_MakeChamfer chamfer(solid);
     for (const auto& edge : edges)
@@ -362,7 +364,7 @@ TopoDS_Shape GeometryEngine::apply_chamfer(const TopoDS_Shape& solid, double dis
 
 TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radius, int edge_id)
 {
-    if (radius <= 0.001) return solid;
+    if (radius <= 0.001) throw std::runtime_error("the fillet radius must be greater than 0");
 
     TopoDS_Edge edge = edge_by_index(solid, edge_id);
     if (edge.IsNull()) throw std::runtime_error("apply_fillet: invalid edge id");
@@ -377,7 +379,7 @@ TopoDS_Shape GeometryEngine::apply_fillet(const TopoDS_Shape& solid, double radi
 
 TopoDS_Shape GeometryEngine::apply_chamfer(const TopoDS_Shape& solid, double distance, int edge_id)
 {
-    if (distance <= 0.001) return solid;
+    if (distance <= 0.001) throw std::runtime_error("the chamfer distance must be greater than 0");
 
     TopoDS_Edge edge = edge_by_index(solid, edge_id);
     if (edge.IsNull()) throw std::runtime_error("apply_chamfer: invalid edge id");