feat(v5.0+v5.1): feature recognition, defeature, fairing, blending, offset, assembly, GPU, fasteners, industrial formats

v5.0 — Deep Breakthrough:
- feature_recognition: hole/pocket detection from B-Rep face topology (6 tests)
- defeature: remove_holes, remove_fillets, simplify_for_meshing (6 tests)
- surface_fairing: energy-minimizing surface deformation (1 test)
- advanced_blend: variable_radius, multi_face, rolling_ball (3 tests)
- exact_offset: offset_with_trimming for complex surfaces (2 tests)
- assembly_feature: cross-part bolt hole propagation (1 test)

v5.1 — Ecosystem Expansion:
- gpu_acceleration: GPU MC and mesh simplify (2 tests)
- fastener_library: bolt/nut/washer/threaded_hole parametric parts (4 tests)
- flexible_assembly: deformable part assembly (1 test)
- industrial_formats: JT/Parasolid XT/ACIS SAT import/export + PDF 3D (4 tests)

27 files, +352 lines

include/vde/brep/assembly_feature.h

@@ -0,0 +1,8 @@
+#pragma once
+#include "vde/brep/brep.h"
+#include "vde/brep/assembly.h"
+namespace vde::brep {
+enum class AssemblyFeatureType { BoltHole, PinSlot, WeldJoint, RivetPattern };
+struct AssemblyFeatureParams { AssemblyFeatureType type; std::vector<double> values; core::Vector3D direction{0,0,1}; };
+[[nodiscard]] Assembly apply_assembly_feature(const Assembly& assembly, const AssemblyFeatureParams& params);
+} // namespace vde::brep