docs: 补全 C# XML 文档注释，覆盖所有公开与内部成员

为 14 个项目中缺少 XML 注释的类、接口、方法、属性、字段、record、
枚举等成员补全中文文档注释。接口方法在接口层定义完整注释，实现类
使用 <inheritdoc /> 引用。私有辅助方法结合业务语义编写注释。

扫描结果：missing-csharp-docs.txt 缺失项归零。
构建结果：0 警告，0 错误。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

FileShare-Services/Services/FileLibrary/FileLibraryEndpointService.cs

@@ -3,49 +3,61 @@ using FileShare_Services.Core;
 
 namespace FileShare_Services.Services.FileLibrary
 {
+    /// <summary>
+    /// 文件库 HTTP 端点服务，将请求适配到 <see cref="IFileLibraryService"/> 并包装为 <see cref="IApiResponse"/>。
+    /// </summary>
     public sealed class FileLibraryEndpointService(IFileLibraryService fileLibrary) : IFileLibraryEndpointService
     {
+        /// <inheritdoc />
         public async Task<IApiResponse> GetDrivesAsync(ServiceEndpointContext ctx)
         {
             return ResponseHelper.Ok(await fileLibrary.GetDrivesAsync());
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> GetDirectoriesAsync(DirectoryQueryRequest request)
         {
             return ResponseHelper.Ok(await fileLibrary.GetDirectoriesAsync(request.Path));
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> GetRootsAsync(ServiceEndpointContext ctx)
         {
             return ResponseHelper.Ok(await fileLibrary.GetRootsAsync());
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> AddRootAsync(AddLibraryRootRequest request)
         {
             return ResponseHelper.Ok(await fileLibrary.AddRootAsync(request), "文件库目录已添加并完成扫描。");
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> SetRootEnabledAsync(UpdateLibraryRootRequest request)
         {
             return ResponseHelper.Ok(await fileLibrary.SetRootEnabledAsync(request), "文件库目录状态已更新。");
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> DeleteRootAsync(DeleteLibraryRootRequest request)
         {
             await fileLibrary.DeleteRootAsync(request);
             return ResponseHelper.Succeed("文件库目录已删除。");
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> ScanRootAsync(ScanLibraryRootRequest request)
         {
             return ResponseHelper.Ok(await fileLibrary.ScanRootAsync(request.Id), "文件库目录扫描完成。");
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> SearchFilesAsync(SearchFilesRequest request)
         {
             return await fileLibrary.SearchFilesAsync(request);
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> GetFileAsync(FileQueryRequest request)
         {
             ValidateFileId(request.Id);
@@ -55,6 +67,7 @@ namespace FileShare_Services.Services.FileLibrary
                 : ResponseHelper.Ok(file);
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> GetTextPreviewAsync(FileQueryRequest request)
         {
             ValidateFileId(request.Id);
@@ -64,6 +77,7 @@ namespace FileShare_Services.Services.FileLibrary
                 : ResponseHelper.Ok(preview);
         }
 
+        /// <inheritdoc />
         public async Task<IApiResponse> BrowseDirectoryAsync(BrowseDirectoryRequest request)
         {
             if (request.RootId <= 0)
@@ -73,6 +87,11 @@ namespace FileShare_Services.Services.FileLibrary
             return ResponseHelper.Ok(result);
         }
 
+        /// <summary>
+        /// 验证文件 ID 是否有效，无效时抛出 <see cref="ArgumentException"/>。
+        /// </summary>
+        /// <param name="id">文件记录 ID。</param>
+        /// <exception cref="ArgumentException">ID 小于等于 0 时抛出。</exception>
         private static void ValidateFileId(int id)
         {
             if (id > 0)