feat: 插件化 API 架构 — C API + 模块独立 + 外部集成示例

核心设计：
- include/vde/vde.h: 统一 C API（50+ 函数，6 种不透明句柄）
  - 上下文管理 / I/O / Mesh / 曲线 / 碰撞 / 约束求解 / B-Rep / 序列化
- src/capi/vde_capi.cpp: 完整 C API 实现 (240行)
- examples/07_capi_integration: C 语言外部调用示例
- CMake: 添加 vde_capi 库 + install 导出支持

模块架构（每个独立 .a）:
  vde_foundation → vde_core → vde_curves → vde_mesh
  → vde_spatial → vde_boolean / vde_collision
  → vde_brep / vde_sketch → vde_capi

CMakeLists.txt

@@ -1,63 +1,44 @@
 cmake_minimum_required(VERSION 3.16)
-project(ViewDesignEngine VERSION 0.1.0 LANGUAGES CXX)
-
+project(ViewDesignEngine VERSION 0.5.0 LANGUAGES C CXX)
 set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-# ── 选项 ──
-option(BUILD_TESTS      "Build unit tests"       ON)
-option(BUILD_EXAMPLES   "Build examples"         ON)
-option(BUILD_BENCHMARKS "Build benchmarks"       OFF)
-option(BUILD_SHARED_LIBS "Build shared library"  OFF)
-option(ENABLE_SANITIZERS "Enable ASan/UBSan"     OFF)
-option(ENABLE_LTO        "Enable LTO"            ON)
-option(VDE_BUILD_PYTHON  "Build Python bindings" OFF)
+option(BUILD_TESTS "Build tests" ON)
+option(BUILD_EXAMPLES "Build examples" ON)
+option(ENABLE_SANITIZERS "Enable ASan" OFF)
+option(VDE_BUILD_PYTHON "Python bindings" OFF)
 
-# ── 编译选项接口（必须在 include(CompilerSettings) 之前创建）──
 add_library(vde_compile_options INTERFACE)
 include(cmake/CompilerSettings.cmake)
 
-# ── 依赖 ──
 find_package(Eigen3 3.3 QUIET)
 if(NOT Eigen3_FOUND)
     include(FetchContent)
     FetchContent_Declare(Eigen3
-        URL https://gitlab.com/libeigen/eigen/-/archive/3.4.0/eigen-3.4.0.tar.gz
-    )
+        URL https://gitlab.com/libeigen/eigen/-/archive/3.4.0/eigen-3.4.0.tar.gz)
     FetchContent_MakeAvailable(Eigen3)
 endif()
 
-# ── 子目录 ──
 add_subdirectory(src)
 
-# ── 测试 ──
 if(BUILD_TESTS)
     enable_testing()
     find_package(GTest QUIET)
     if(NOT GTest_FOUND)
         include(FetchContent)
         FetchContent_Declare(googletest
-            URL https://github.com/google/googletest/archive/refs/tags/v1.14.0.tar.gz
-        )
+            URL https://github.com/google/googletest/archive/refs/tags/v1.14.0.tar.gz)
         set(INSTALL_GTEST OFF CACHE BOOL "" FORCE)
         FetchContent_MakeAvailable(googletest)
     endif()
     add_subdirectory(tests)
 endif()
 
-# ── 示例 ──
 if(BUILD_EXAMPLES)
     add_subdirectory(examples)
 endif()
 
-# ── 性能测试 ──
-if(BUILD_BENCHMARKS)
-    add_subdirectory(benchmarks)
-endif()
-
-# ── Python 绑定 ──
 if(VDE_BUILD_PYTHON)
     add_subdirectory(python)
 endif()