Add metadata validation script and module documentation

- Introduced a new Python script `check_agents_metadata.py` for validating agent metadata, including YAML parsing, rating ranges, and cross-references.
- Added usage instructions and exit codes for the script.
- Created a new markdown file `模块目录和功能说明.md` to outline the directory structure and functionality of the modules.
- Added a text file `说明此文件不可AI修改.txt` to specify that certain files should not be modified by AI, including important information about the `dstalk` framework and its modules.

tests/service_registry_test.cpp

@@ -1,9 +1,10 @@
-// ============================================================================
-// service_registry_test.cpp — ServiceRegistry 单元测试（补充覆盖，不与 host_api_test 重叠）
-// ============================================================================
-// host_api_test 已覆盖: 重复注册(同名同版/同名异版)、查询不存在服务、版本不满足、
-//                      shutdown 后查询。本测试补充边界与生命周期路径。
-// ============================================================================
+/*
+ * @file service_registry_test.cpp
+ * @brief ServiceRegistry unit tests (supplement to host_api_test): register,
+ *        query, version check, unregister, null-pointer safety, re-registration.
+ * ServiceRegistry 单元测试（host_api_test 补充）：注册、查询、版本检查、取消注册、空指针安全、重新注册。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
 
 #include <cstring>
 #include <iostream>
@@ -12,6 +13,7 @@
 
 // ---- 轻量断言 ----
 static int g_failures = 0;
+// Lightweight assertion helper: increments g_failures counter on failure
 #define TCHECK(cond, msg) do {                            \
     if (cond) {                                           \
         std::cout << "[OK] " << (msg) << "\n";            \
@@ -21,7 +23,11 @@ static int g_failures = 0;
     }                                                     \
 } while (0)
 
-// ============================================================
+// ServiceRegistry 补充测试：空名称/虚表拒绝、完整生命周期（注册→查询→取消注册→查询为空）、
+// 取消注册空指针安全、取消注册后重新注册、空名称查询。
+// ServiceRegistry supplement tests: null-name/vtable rejection, full lifecycle
+// (register->query->unregister->query nullptr), unregister nullptr safety,
+// re-registration after unregister, and query with nullptr name.
 int main()
 {
     std::cout << "=== dstalk service_registry unit tests (supplement) ===\n\n";
@@ -47,6 +53,7 @@ int main()
 
     // ====================================================================
     // Test 3: 完整生命周期 — register → query → unregister → query(nullptr)
+    // Test 3: full lifecycle — register → query → unregister → query(nullptr)
     // ====================================================================
     {
         dstalk::ServiceRegistry reg;
@@ -66,6 +73,7 @@ int main()
 
     // ====================================================================
     // Test 4: unregister_service(nullptr name) 不崩溃（安全空操作）
+    // Test 4: unregister_service(nullptr name) does not crash (safe no-op)
     // ====================================================================
     {
         dstalk::ServiceRegistry reg;
@@ -75,6 +83,7 @@ int main()
 
     // ====================================================================
     // Test 5: 注册后重新注册同名 → 先 unregister 再 register 成功
+    // Test 5: re-register same name after unregister → succeeds
     // ====================================================================
     {
         dstalk::ServiceRegistry reg;
@@ -101,7 +110,7 @@ int main()
     }
 
     // ====================================================================
-    // 结果
+    // 结果 / Result
     // ====================================================================
     std::cout << "\n";
     if (g_failures == 0) {