Mirror CAD persistence (K1+K2+G1) from snaporca-cad onto mainline OrcaSlicer

Dual-fork mandate: port the parametric-recipe 3MF persistence from
snaporca-cad commits ed19eac+147e1c4 so a saved project reopens with the
editable CAD feature tree, not just the baked mesh.

Shared kernel/format/GUI (identical to snaporca-cad):
- CadDocument serialize_recipe/deserialize_recipe (cereal BinaryArchive,
  versioned) + CadFeature split save/load + imported_solid<->BRep string.
- Model::cad_recipe carried through 3MF zip entry Metadata/SnapOrca_cad.bin
  (writer + binary-verbatim reader branch).
- DesignPanel on_commit() stamps the recipe; on_tab_shown() rehydrates a
  loaded project via load_recipe() (deserialize -> feed_bodies + refresh_tree).

Mainline-only adapters (no snaporca-cad counterpart — Catch2 v3 vs v2):
- tests/libslic3r/test_caddocument.cpp: <catch2/catch_all.hpp> +
  `using Catch::Approx;` (v3 scopes Approx under Catch::).
- tests/libslic3r/CMakeLists.txt: register test_caddocument.cpp (the
  original CAD port had left it out of the test build).

Verified on behemoth (snaporca-deps toolchain): libslic3r_tests clean;
[CadDocument] 17/18 (only the pre-existing tangent-to-circle SIGABRT fails,
identical to snaporca-tkz); K1 serialize round-trip + version-reject pass
(13 assertions); new [3mf] "CAD recipe blob survives a 3mf save/load cycle"
passes byte-for-byte; orca-slicer GUI links clean (186/186, DesignPanel.cpp
compiled). Interactive :10 click-through pending (no Design-tab automation).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BVzKmX6Y1aEteit1HTXG4Q

src/libslic3r/Format/3mf.cpp

@@ -73,6 +73,7 @@ const std::string THUMBNAIL_FILE = "Metadata/thumbnail.png";
 const std::string PRINT_CONFIG_FILE = "Metadata/Slic3r_PE.config";
 const std::string MODEL_CONFIG_FILE = "Metadata/Slic3r_PE_model.config";
 const std::string LAYER_HEIGHTS_PROFILE_FILE = "Metadata/Slic3r_PE_layer_heights_profile.txt";
+const std::string CAD_RECIPE_FILE = "Metadata/SnapOrca_cad.bin";
 const std::string LAYER_CONFIG_RANGES_FILE = "Metadata/Prusa_Slicer_layer_config_ranges.xml";
 const std::string SLA_SUPPORT_POINTS_FILE = "Metadata/Slic3r_PE_sla_support_points.txt";
 const std::string SLA_DRAIN_HOLES_FILE = "Metadata/Slic3r_PE_sla_drain_holes.txt";
@@ -805,6 +806,17 @@ ModelVolumeType type_from_string(const std::string &s)
                         return false;
                     }
                 }
+                if (boost::algorithm::iequals(name, CAD_RECIPE_FILE)) {
+                    if (stat.m_uncomp_size > 0) {
+                        std::string buffer((size_t)stat.m_uncomp_size, 0);
+                        if (mz_zip_reader_extract_file_to_mem(&archive, stat.m_filename,
+                                (void*)buffer.data(), (size_t)stat.m_uncomp_size, 0) != 0) {
+                            model.cad_recipe = std::move(buffer);
+                        } else {
+                            add_error("Error while reading CAD recipe data");
+                        }
+                    }
+                }
             }
         }
 
@@ -2317,6 +2329,7 @@ ModelVolumeType type_from_string(const std::string &s)
         bool _add_mesh_to_object_stream(mz_zip_writer_staged_context &context, ModelObject& object, VolumeToOffsetsMap& volumes_offsets);
         bool _add_build_to_model_stream(std::stringstream& stream, const BuildItemsList& build_items);
         bool _add_layer_height_profile_file_to_archive(mz_zip_archive& archive, Model& model);
+        bool _add_cad_recipe_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_layer_config_ranges_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_sla_support_points_file_to_archive(mz_zip_archive& archive, Model& model);
         bool _add_sla_drain_holes_file_to_archive(mz_zip_archive& archive, Model& model);
@@ -2387,6 +2400,13 @@ ModelVolumeType type_from_string(const std::string &s)
             return false;
         }
 
+        // Adds CAD recipe file ("Metadata/SnapOrca_cad.bin").
+        if (!_add_cad_recipe_file_to_archive(archive, model)) {
+            close_zip_writer(&archive);
+            boost::filesystem::remove(filename);
+            return false;
+        }
+
         // Adds layer config ranges file ("Metadata/Slic3r_PE_layer_config_ranges.txt").
         // All layer height profiles of all ModelObjects are stored here, indexed by 1 based index of the ModelObject in Model.
         // The index differes from the index of an object ID of an object instance of a 3MF file!
@@ -2919,6 +2939,19 @@ ModelVolumeType type_from_string(const std::string &s)
         return true;
     }
 
+    bool _3MF_Exporter::_add_cad_recipe_file_to_archive(mz_zip_archive& archive, Model& model)
+    {
+        if (model.cad_recipe.empty())
+            return true;
+        if (!mz_zip_writer_add_mem(&archive, CAD_RECIPE_FILE.c_str(),
+                (const void*)model.cad_recipe.data(), model.cad_recipe.length(),
+                MZ_DEFAULT_COMPRESSION)) {
+            add_error("Unable to add CAD recipe file to archive");
+            return false;
+        }
+        return true;
+    }
+
     bool _3MF_Exporter::_add_layer_config_ranges_file_to_archive(mz_zip_archive& archive, Model& model)
     {
         std::string out = "";