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/file_io/CMakeLists.txt

@@ -0,0 +1,9 @@
+add_library(plugin-file_io SHARED src/file_io_plugin.cpp)
+
+target_link_libraries(plugin-file_io PRIVATE dstalk)
+
+set_target_properties(plugin-file_io PROPERTIES
+    PREFIX ""
+    LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/plugins"
+    RUNTIME_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/plugins"
+)

plugins_base/file_io/src/file_io_plugin.cpp

@@ -0,0 +1,107 @@
+/*
+ * @file file_io_plugin.cpp
+ * @brief File I/O plugin: basic file read/write service.
+ * 文件 I/O 插件：基本文件读写服务。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
+
+#include "dstalk/dstalk_host.h"
+#include "dstalk/dstalk_services.h"
+
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+
+// ============================================================
+// 全局状态 / Global state
+// ============================================================
+static const dstalk_host_api_t* g_host = nullptr;
+
+// ============================================================
+// 服务实现 / Service implementations
+// ============================================================
+// 读取文件全部内容到主机分配的缓冲区，调用方须通过 host->free 释放 / Read the entire contents of a file into a host-allocated buffer. Caller must free via host->free.
+static int file_read(const char* path, char** content) {
+    if (!path || !content) return -1;
+
+    FILE* fp = fopen(path, "rb");
+    if (!fp) return -1;
+
+    // 获取文件大小 / Get file size
+    fseek(fp, 0, SEEK_END);
+    long fsize = ftell(fp);
+    fseek(fp, 0, SEEK_SET);
+
+    if (fsize < 0) {
+        fclose(fp);
+        return -1;
+    }
+
+    // 通过主机分配器分配缓冲区（+1 用于空终止符） / Allocate buffer via host allocator (+1 for null terminator)
+    char* buf = (char*)g_host->alloc((size_t)fsize + 1);
+    if (!buf) {
+        fclose(fp);
+        return -1;
+    }
+
+    size_t read_bytes = fread(buf, 1, (size_t)fsize, fp);
+    fclose(fp);
+
+    if (read_bytes != (size_t)fsize) {
+        g_host->free(buf);
+        return -1;
+    }
+
+    buf[read_bytes] = '\0';
+    *content = buf;
+    return 0;
+}
+
+// 将字符串写入文件，覆盖已有内容 / Write a string to a file, overwriting any existing content.
+static int file_write(const char* path, const char* content) {
+    if (!path || !content) return -1;
+
+    FILE* fp = fopen(path, "wb");
+    if (!fp) return -1;
+
+    size_t len = strlen(content);
+    size_t written = fwrite(content, 1, len, fp);
+    fclose(fp);
+
+    return (written == len) ? 0 : -1;
+}
+
+static dstalk_file_io_service_t g_service = {
+    file_read,
+    file_write
+};
+
+// ============================================================
+// 插件生命周期 / Plugin lifecycle
+// ============================================================
+// 插件初始化：保存主机指针并注册 file_io 服务 / Plugin init: store host pointer and register the file_io service.
+static int on_init(const dstalk_host_api_t* host) {
+    g_host = host;
+    return host->register_service("file_io", 1, &g_service);
+}
+
+// 插件关闭：无需清理 / Plugin shutdown: nothing to clean up.
+static void on_shutdown() {
+    // 无需清理 / nothing to clean up
+}
+
+static dstalk_plugin_info_t g_info = {
+    "file_io",             // name 名称
+    "1.0.0",               // version 版本
+    "Basic file I/O service",  // description 描述
+    DSTALK_API_VERSION,    // api_version
+    {nullptr},             // dependencies 依赖 (none)
+    on_init,               // on_init
+    on_shutdown,           // on_shutdown
+    nullptr                // on_event
+};
+
+// 必须入口点：返回插件描述符给主机 / Mandatory entry point: returns the plugin descriptor to the host.
+extern "C" DSTALK_PLUGIN_EXPORT dstalk_plugin_info_t* dstalk_plugin_init(void) {
+    return &g_info;
+}