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.

plugins_base/CMakeLists.txt

@@ -0,0 +1,7 @@
+# ============================================================
+# 基础插件（无依赖） / Base plugins (no dependencies)
+# ============================================================
+
+add_subdirectory(config)
+add_subdirectory(file_io)
+add_subdirectory(lsp)