obsidian-mcp: 初次落地 Obsidian Vault MCP Server (.NET 10, read+write)

把 Obsidian vault 通过 MCP 暴露给 Claude.ai，OAuth 走 nas-auth。
设计文档见 vault Coding/obsidian-mcp/obsidian-mcp 设计.md。
代码层落地参考 vault Coding/obsidian-mcp/MCP 实现指南.md。

V1+V2 同时实现（用户要求跳过分阶段直接全部）：

读 Tools（需 scope=read:obsidian）：
- list_vault_tree（一次性 vault 地图，限制深度）
- list_files / read_file（含 offset/limit 大文件分页）
- search（子串匹配 + glob 过滤，最多 50 hits）
- get_metadata（size / modified_at / has_frontmatter）

写 Tools（需 scope=write:obsidian）：
- write_file / append_file
- 多重门禁：scope 校验 + 路径黑名单 + 写入白名单 + 永禁文件
  - 永禁写：任意目录的 AGENTS.md / PROFILE.md / README.md / CLAUDE.md / 01-Secret/**
  - 白名单：02-ShengquGames/logs/ + Coding/ + NAS/NAS 待办清单.md
- 写入审计日志按天 rotate（JSON line）

安全：
- VaultPathResolver chroot：path traversal + symlink 双拒绝
- JwtBearer (HS256, Current+Previous fallback, MapInboundClaims=false)
- aud=obsidian, iss=https://auth.zhengchentao.win
- 黑名单：01-Secret / .obsidian / .trash / .git

技术栈：
- .NET 10 + ModelContextProtocol SDK 1.0
- Streamable HTTP transport (POST /mcp)
- JwtBearer 10.0 + IdentityModel.Tokens 8.x

部署：
- Dockerfile multi-stage，runtime 装 ripgrep（V3 备用），non-root user
- .gitea/workflows/build-image.yml：build + deploy 双 job，buildkit v0.13.2
- 容器内 :8080，宿主端口 9090
- 子域名 obs.zhengchentao.win
- vault 挂载 /volume1/docker/webdav/data/Zhengchen:/vault:rw（V2 写入需要 rw）

测试：35/35 单测过（VaultPathResolver path traversal/blacklist/symlink + VaultWriteGuard whitelist/forbidden）

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

Tools/GetMetadataTool.cs

@@ -0,0 +1,60 @@
+using System.ComponentModel;
+using ModelContextProtocol.Server;
+using ObsidianMcp.Auth;
+using ObsidianMcp.Services;
+
+namespace ObsidianMcp.Tools;
+
+[McpServerToolType]
+public class GetMetadataTool(VaultPathResolver resolver, IHttpContextAccessor http)
+{
+    [McpServerTool]
+    [Description(
+        "Get metadata for a vault file without reading its content. " +
+        "Returns size in bytes, last modified timestamp (UTC ISO-8601), " +
+        "and whether the file starts with YAML frontmatter (--- ... ---). " +
+        "Useful for deciding whether to read a file (staleness check, size guard before read_file).")]
+    public FileMetadata GetMetadata(
+        [Description("Vault-relative path to the file. " +
+                     "e.g. 'NAS/NAS 总览.md'")] string path)
+    {
+        ToolScopeGuard.EnsureScope(http, ScopePolicies.ReadObsidian);
+
+        var absPath = resolver.Resolve(path);
+
+        if (!File.Exists(absPath))
+            throw new FileNotFoundException($"文件不存在：{path}");
+
+        var fi = new FileInfo(absPath);
+
+        // 简单判断是否有 frontmatter：读前 4 字节检查是否以 --- 开头
+        bool hasFrontmatter = false;
+        try
+        {
+            using var fs = File.OpenRead(absPath);
+            var header = new byte[4];
+            if (fs.Read(header, 0, 4) == 4)
+                hasFrontmatter = header[0] == '-' && header[1] == '-' && header[2] == '-';
+        }
+        catch
+        {
+            // 读取失败不影响其他字段
+        }
+
+        return new FileMetadata
+        {
+            Path = path,
+            SizeBytes = fi.Length,
+            ModifiedAt = fi.LastWriteTimeUtc.ToString("O"),
+            HasFrontmatter = hasFrontmatter,
+        };
+    }
+}
+
+public class FileMetadata
+{
+    public string Path { get; set; } = "";
+    public long SizeBytes { get; set; }
+    public string ModifiedAt { get; set; } = "";
+    public bool HasFrontmatter { get; set; }
+}