feat: add OpenAI-compatible AI provider plugin with SSE streaming support

- Implemented the OpenAI-compatible AI provider plugin, including configuration, chat, and chat_stream functionalities.
- Added support for SSE streaming and tool calls.
- Integrated Boost.JSON for JSON handling.
- Created CMake configuration for the plugin.
- Added error handling and logging throughout the plugin.

tests/smoke_test.cpp

@@ -58,7 +58,7 @@ int main()
                << "model = \"gpt-4o\"\n";
     }
 
-    // 初始化主机（会自动扫描 plugins/ 加载插件）/ Init host (auto-scans plugins/ to load plugins)
+    // 初始化主机（会自动扫描 plugins_base/middle/upper 加载插件）/ Init host (auto-scans plugins_base/middle/upper to load plugins)
     if (dstalk_init(config_path.string().c_str()) != 0) {
         std::cerr << "dstalk_init failed\n";
         return 1;
@@ -112,7 +112,7 @@ int main()
             return 1;
         }
     } else {
-        std::cerr << "[WARN] file_io service not found (plugin may not be in plugins/ dir)\n";
+        std::cerr << "[WARN] file_io service not found (plugin may not be in plugins_base/ dir)\n";
     }
 
     // 测试服务查询: session / Test service query: session