feat(v3.9): parallel OpenMP boolean + assembly instancing + update notifier

include/vde/brep/assembly_instance.h

@@ -0,0 +1,56 @@
+#pragma once
+#include "vde/brep/assembly.h"
+#include <unordered_map>
+#include <string>
+#include <vector>
+
+namespace vde::brep {
+
+/// Shared geometry instance (for repeated parts)
+struct GeometryInstance {
+    std::string part_name;
+    BrepModel geometry;   ///< shared geometry data
+    size_t use_count = 0; ///< number of references to this geometry
+};
+
+/**
+ * @brief Instance manager for large assemblies.
+ *
+ * Deduplicates repeated parts by reusing shared geometry.
+ * Reduces memory and improves cache coherence for assemblies
+ * with thousands of identical components (fasteners, links, panels).
+ *
+ * @ingroup brep
+ */
+class AssemblyInstancer {
+public:
+    /**
+     * @brief Register a geometry for instancing.
+     * @param name  Part name identifier
+     * @param geom  Geometry to register
+     * @return instance ID, reuses existing if same name & geometry matches
+     */
+    int register_instance(const std::string& name, const BrepModel& geom);
+
+    /**
+     * @brief Create an occurrence of a registered instance.
+     * @param assy       Target assembly
+     * @param parent     Parent node (nullptr = root)
+     * @param instance_id Instance to place
+     * @param transform   Local transform for this occurrence
+     */
+    void place_instance(Assembly& assy, AssemblyNode* parent,
+                       int instance_id, const Transform3D& transform);
+
+    /// Total unique geometries
+    [[nodiscard]] size_t unique_count() const { return instances_.size(); }
+
+    /// Total placed occurrences
+    [[nodiscard]] size_t total_placed() const { return total_placed_; }
+
+private:
+    std::vector<GeometryInstance> instances_;
+    size_t total_placed_ = 0;
+};
+
+} // namespace vde::brep

include/vde/brep/update_notifier.h

@@ -0,0 +1,41 @@
+#pragma once
+#include "vde/brep/feature_tree.h"
+#include <functional>
+#include <string>
+#include <vector>
+
+namespace vde::brep {
+
+/// Callback type for model changes.
+/// Receives the feature name and the new model after rebuild.
+using UpdateCallback = std::function<void(const std::string& feature_name, const BrepModel& new_model)>;
+
+/**
+ * @brief Notifies listeners when features change.
+ *
+ * Integrates with FeatureHistory: after each apply/undo/redo,
+ * call notify() to push the updated model to all registered callbacks.
+ *
+ * @ingroup brep
+ */
+class UpdateNotifier {
+public:
+    /// Register a callback. Called on every notify().
+    void on_update(UpdateCallback cb) { callbacks_.push_back(std::move(cb)); }
+
+    /// Notify all registered listeners.
+    void notify(const std::string& feature, const BrepModel& model) {
+        for (auto& cb : callbacks_) cb(feature, model);
+    }
+
+    /// Remove all callbacks.
+    void clear() { callbacks_.clear(); }
+
+    /// Number of registered callbacks.
+    [[nodiscard]] size_t listener_count() const { return callbacks_.size(); }
+
+private:
+    std::vector<UpdateCallback> callbacks_;
+};
+
+} // namespace vde::brep