feat(v4.6): memory pool + parallel boolean/MC/intersection + GMP exact predicates

M1 — Memory Pool (内存池):
- ObjectPool<T>: O(1) acquire/release with free-list, chunk-based expansion
- ThreadSafeObjectPool<T>: per-thread local pools with global fallback
- CowPtr<T>: copy-on-write smart pointer with shallow/deep copy
- 10 tests: single/multi-thread, CoW detach, reuse rate

M2 — Parallel Boolean (并行布尔):
- parallel_face_face_intersection(): OpenMP face-pair dispatch with AABB culling
- parallel_classify_faces(): thread-safe ray casting classification
- parallel_mesh_union/intersection/difference + B-Rep variants
- Thread count management API
- 12 tests: coverage, empty cases, identity operations

M3 — Parallel Marching Cubes (并行MC):
- parallel_marching_cubes(): Z-slice parallel voxel processing
- parallel_adaptive_mc(): octree-based adaptive resolution
- Complete 256-entry edge table + Möller-Trumbore interpolation
- 5 tests: sphere basic/high-res/empty/adaptive/threaded

M4 — Parallel Surface Intersection (并行求交):
- parallel_curve_intersections(): per-pair parallel dispatch
- parallel_surface_intersection(): recursive subdivision + Newton refinement
- AABB broad-phase culling before narrow-phase
- 4 tests: curve pairs, surface batch

M5 — GMP Exact Predicates (精确谓词):
- exact_orient2d/3d: adaptive precision (double → GMP fallback)
- exact_in_sphere: circumsphere test with degenerate handling
- exact_point_in_polygon/polyhedron: robust ray casting
- PrecisionMode: Fast/Adaptive/Exact with global toggle
- 12 tests: all orientations, boundary cases, mode switching

21 files, +2263 lines

include/vde/curves/parallel_intersection.h

@@ -0,0 +1,84 @@
+#pragma once
+/**
+ * @file parallel_intersection.h
+ * @brief 并行曲面/曲线求交
+ *
+ * OpenMP 并行化曲面-曲面求交和曲线-曲线求交。
+ *
+ * @ingroup curves
+ */
+
+#include "vde/core/point.h"
+#include "vde/curves/nurbs_curve.h"
+#include "vde/curves/nurbs_surface.h"
+#include <vector>
+#include <utility>
+
+namespace vde::curves {
+
+// ═══════════════════════════════════════════════════════════
+//  Parallel Curve Intersection
+// ═══════════════════════════════════════════════════════════
+
+/**
+ * @brief 并行计算一组曲线对的交点
+ *
+ * 每对曲线独立求交，结果线程安全合并。
+ *
+ * @param curve_pairs 曲线对列表 ((curve_a_idx, curve_b_idx), ...)
+ * @param curves_a 曲线集合 A
+ * @param curves_b 曲线集合 B
+ * @return 每条曲线对的交点参数列表
+ */
+[[nodiscard]] std::vector<std::vector<std::pair<double, double>>>
+parallel_curve_intersections(
+    const std::vector<std::pair<int, int>>& curve_pairs,
+    const std::vector<NurbsCurve>& curves_a,
+    const std::vector<NurbsCurve>& curves_b);
+
+// ═══════════════════════════════════════════════════════════
+//  Parallel Surface Intersection
+// ═══════════════════════════════════════════════════════════
+
+/// 曲面交线段
+struct SurfaceIntersectionSegment {
+    core::Point3D start;
+    core::Point3D end;
+    double u_a_start, v_a_start;
+    double u_a_end, v_a_end;
+    double u_b_start, v_b_start;
+    double u_b_end, v_b_end;
+};
+
+/**
+ * @brief 并行计算两曲面的交线
+ *
+ * 递归细分 + 牛顿精化，边界盒预筛选，并行分发。
+ *
+ * @param surf_a 曲面 A
+ * @param surf_b 曲面 B
+ * @param tolerance 精度要求
+ * @param max_refinements 最大细分次数
+ * @return 交线段列表
+ */
+[[nodiscard]] std::vector<SurfaceIntersectionSegment>
+parallel_surface_intersection(
+    const NurbsSurface& surf_a, const NurbsSurface& surf_b,
+    double tolerance = 1e-6, int max_refinements = 10);
+
+/**
+ * @brief 并行批量曲面-曲面对求交
+ *
+ * @param pairs 曲面对索引
+ * @param surfaces_a 曲面集合 A
+ * @param surfaces_b 曲面集合 B
+ * @return 每对曲面的交线段列表
+ */
+[[nodiscard]] std::vector<std::vector<SurfaceIntersectionSegment>>
+parallel_surface_intersections(
+    const std::vector<std::pair<int, int>>& pairs,
+    const std::vector<NurbsSurface>& surfaces_a,
+    const std::vector<NurbsSurface>& surfaces_b,
+    double tolerance = 1e-6);
+
+} // namespace vde::curves