✨ feat(native-planning): 添加 Rust ICSP 原生规划核心及 C# 互操作集成

* 新增 Rust 原生 ICSP 规划库 (Cargo 项目, CubicSpline 算法, FFI 接口)
* 新增 Flyshot.Native.Planning C# 互操作项目 (P/Invoke 封装)
* 更新 ControllerClientCompat 适配新的规划接口
* 添加构建脚本 (Copy-NativePlanningArtifacts.ps1)
* 新增互操作测试及一致性对比测试
* 更新解决方案文件和设计文档

src/Flyshot.Native.Planning/NativeIcspMethods.cs

@@ -0,0 +1,130 @@
+using System.Runtime.InteropServices;
+
+namespace Flyshot.Native.Planning;
+
+/// <summary>
+/// 声明 Rust 原生规划库导出的稳定 C ABI 方法。
+/// </summary>
+internal static partial class NativeIcspMethods
+{
+    /// <summary>
+    /// 保护原生库句柄首次初始化，避免并发规划重复加载。
+    /// </summary>
+    private static readonly object LibraryLoadLock = new();
+
+    /// <summary>
+    /// 保存已加载原生库句柄，使 P/Invoke 生命周期覆盖整个进程。
+    /// </summary>
+    private static nint _libraryHandle;
+
+    /// <summary>
+    /// 保存当前进程已绑定到 P/Invoke 逻辑名称的实际库路径。
+    /// </summary>
+    private static string? _loadedLibraryPath;
+
+    /// <summary>
+    /// 初始化程序集级 DllImport 解析器，把逻辑库名绑定到显式加载句柄。
+    /// </summary>
+    static NativeIcspMethods()
+    {
+        NativeLibrary.SetDllImportResolver(
+            typeof(NativeIcspMethods).Assembly,
+            ResolveImportedLibrary);
+    }
+
+    /// <summary>
+    /// 使用指定解析器确保原生规划库已加载。
+    /// </summary>
+    /// <param name="resolver">负责生成平台路径并加载原生库的解析器。</param>
+    internal static void EnsureLibraryLoaded(NativePlanningLibraryResolver resolver)
+    {
+        ArgumentNullException.ThrowIfNull(resolver);
+        string requestedPath = resolver.ResolveLibraryPath();
+
+        lock (LibraryLoadLock)
+        {
+            if (_libraryHandle != nint.Zero)
+            {
+                StringComparison comparison = OperatingSystem.IsWindows()
+                    ? StringComparison.OrdinalIgnoreCase
+                    : StringComparison.Ordinal;
+                if (!string.Equals(_loadedLibraryPath, requestedPath, comparison))
+                {
+                    throw new NativePlanningException(
+                        $"Rust 原生规划库已绑定到“{_loadedLibraryPath}”，不能在同一进程中改为“{requestedPath}”。",
+                        errorCode: -1008);
+                }
+
+                return;
+            }
+
+            _libraryHandle = resolver.LoadLibrary();
+            _loadedLibraryPath = requestedPath;
+        }
+    }
+
+    /// <summary>
+    /// 调用 Rust ICSP 入口并返回错误码和结果指针。
+    /// </summary>
+    /// <param name="waypoints">行优先连续路点数组。</param>
+    /// <param name="waypointCount">路点数量。</param>
+    /// <param name="degreesOfFreedom">每个路点的关节自由度。</param>
+    /// <param name="velocityLimits">逐关节速度上限。</param>
+    /// <param name="accelerationLimits">逐关节加速度上限。</param>
+    /// <param name="jerkLimits">逐关节 jerk 上限。</param>
+    /// <param name="options">与 Rust C ABI 对齐的规划选项。</param>
+    /// <param name="result">接收 Rust 分配的结果指针。</param>
+    /// <returns>零表示成功，非零表示固定类别的原生错误。</returns>
+    [LibraryImport(
+        NativePlanningLibraryResolver.LogicalLibraryName,
+        EntryPoint = "flyshot_icsp_plan")]
+    internal static unsafe partial int FlyshotIcspPlan(
+        double* waypoints,
+        int waypointCount,
+        int degreesOfFreedom,
+        double* velocityLimits,
+        double* accelerationLimits,
+        double* jerkLimits,
+        NativeIcspOptions* options,
+        out nint result);
+
+    /// <summary>
+    /// 释放由 Rust 分配的 ICSP 结果对象。
+    /// </summary>
+    /// <param name="result">Rust 返回的结果对象指针；允许为空指针。</param>
+    [LibraryImport(
+        NativePlanningLibraryResolver.LogicalLibraryName,
+        EntryPoint = "flyshot_icsp_result_free")]
+    internal static partial void FlyshotIcspResultFree(nint result);
+
+    /// <summary>
+    /// 获取当前线程最近一次 Rust 调用保存的 UTF-8 错误文本。
+    /// </summary>
+    /// <returns>指向线程局部 C 字符串的只读指针。</returns>
+    [LibraryImport(
+        NativePlanningLibraryResolver.LogicalLibraryName,
+        EntryPoint = "flyshot_last_error_message")]
+    internal static partial nint FlyshotLastErrorMessage();
+
+    /// <summary>
+    /// 将固定逻辑库名解析为已经显式加载的系统句柄。
+    /// </summary>
+    /// <param name="libraryName">P/Invoke 请求的逻辑库名。</param>
+    /// <param name="assembly">发起请求的托管程序集。</param>
+    /// <param name="searchPath">调用方提供的可选搜索路径。</param>
+    /// <returns>逻辑名称匹配时返回已加载句柄，否则返回零交给系统继续解析。</returns>
+    private static nint ResolveImportedLibrary(
+        string libraryName,
+        System.Reflection.Assembly assembly,
+        DllImportSearchPath? searchPath)
+    {
+        _ = assembly;
+        _ = searchPath;
+        return string.Equals(
+            libraryName,
+            NativePlanningLibraryResolver.LogicalLibraryName,
+            StringComparison.Ordinal)
+            ? _libraryHandle
+            : nint.Zero;
+    }
+}