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.

dstalk_core/src/service_registry.hpp

@@ -0,0 +1,46 @@
+/* @file service_registry.hpp
+ * @brief Name-versioned service registry for decoupled plugin communication.
+ * 基于名称+版本的服务注册表，用于插件间解耦通信。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
+
+#pragma once
+
+#include <mutex>
+#include <shared_mutex>
+#include <string>
+#include <unordered_map>
+
+namespace dstalk {
+
+// 名称 + 最低版本服务目录 / Name + minimum-version service directory.
+// 插件注册 vtable；消费者按名称和版本约束查询 /
+// Plugins register vtables; consumers query by name and version constraint.
+// 读取（query）使用 shared_lock；写入（register/unregister）使用 unique_lock /
+// Reads (query) use shared_lock; writes (register/unregister) use unique_lock.
+class ServiceRegistry {
+public:
+    ServiceRegistry() = default;
+    ~ServiceRegistry() = default;
+
+    // 注册服务 / Register a named service at a given version
+    int register_service(const char* name, int version, void* vtable);
+
+    // 查询服务（返回 vtable 指针，或 nullptr）/ Query a service by name and minimum version
+    void* query_service(const char* name, int min_version) const;
+
+    // 注销服务 / Unregister a named service
+    void unregister_service(const char* name);
+
+private:
+    struct ServiceEntry {
+        std::string name;
+        int version;
+        void* vtable;
+    };
+
+    mutable std::shared_mutex mutex_;            // 读写锁：query 用 shared，register/unregister 用 unique / RW lock: shared for query, unique for register/unregister
+    std::unordered_map<std::string, ServiceEntry> services_;
+};
+
+} // namespace dstalk