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/config/CMakeLists.txt

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

plugins_base/config/include/toml_parse.h

@@ -0,0 +1,75 @@
+/*
+ * @file toml_parse.h
+ * @brief Lightweight single-header TOML parser (subset: flat key-value pairs).
+ * 轻量级单头文件 TOML 解析器（子集：扁平键值对）。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
+
+#pragma once
+// 共享 TOML 解析器 —— 由 ConfigStore（核心）和 config 插件共同使用 / Shared TOML parser — used by both ConfigStore (core) and config plugin.
+// W12.2: Extracted from config_store.cpp:23-61 and config_plugin.cpp:28-66
+//        to eliminate the 74-line code duplication (W11.2 audit Finding 1).
+// Does NOT support: inline tables, arrays, multi-line strings, escape sequences.
+// 不支持：内联表、数组、多行字符串、转义序列。
+
+#include <string>
+
+namespace dstalk {
+namespace toml {
+
+/// 解析 TOML 字符串，对每个键值对调用 on_kv(full_key, value) / Parse a TOML string, calling on_kv(full_key, value) for each key-value pair.
+/// 支持 [section] 标题、key = "value" 键值对、# 注释、空行 / Supports [section] headers, key = "value" pairs, # comments, blank lines.
+template<typename F>
+inline void parse(const std::string& content, F&& on_kv)
+{
+    std::string current_section;
+    size_t pos = 0;
+
+    while (pos < content.size()) {
+        // 去除左侧空白 / Trim left whitespace
+        while (pos < content.size() && (content[pos] == ' ' || content[pos] == '\t'))
+            pos++;
+        if (pos >= content.size()) break;
+
+        // 提取下一行 / Extract next line
+        size_t nl = content.find('\n', pos);
+        std::string line = (nl != std::string::npos)
+            ? content.substr(pos, nl - pos) : content.substr(pos);
+        pos = (nl != std::string::npos) ? nl + 1 : content.size();
+
+        // 去除右侧空白（包括 \r） / Trim right whitespace (including \r)
+        while (!line.empty() && (line.back() == '\r' || line.back() == ' '))
+            line.pop_back();
+
+        // 跳过空行和注释 / Skip empty lines and comments
+        if (line.empty() || line[0] == '#') continue;
+
+        // 节标题: [section_name] / Section header: [section_name]
+        if (line[0] == '[' && line.back() == ']') {
+            current_section = line.substr(1, line.size() - 2);
+            continue;
+        }
+
+        // 键 = 值 / Key = value
+        size_t eq = line.find('=');
+        if (eq == std::string::npos) continue;
+
+        std::string key = line.substr(0, eq);
+        while (!key.empty() && key.back() == ' ') key.pop_back();
+        if (key.empty()) continue;
+
+        std::string val = line.substr(eq + 1);
+        while (!val.empty() && (val.front() == ' ' || val.front() == '\t'))
+            val.erase(0, 1);
+        if (val.size() >= 2 && val.front() == '"' && val.back() == '"')
+            val = val.substr(1, val.size() - 2);
+
+        std::string full_key = current_section.empty()
+            ? key : current_section + "." + key;
+
+        on_kv(full_key, val);
+    }
+}
+
+} // namespace toml
+} // namespace dstalk

plugins_base/config/src/config_plugin.cpp

@@ -0,0 +1,110 @@
+/*
+ * @file config_plugin.cpp
+ * @brief Config plugin: TOML file parsing and key-value configuration service.
+ * 配置插件：TOML 文件解析和键值配置服务。
+ * Copyright (c) 2026 dstalk contributors. GPLv3.
+ */
+
+#include "dstalk/dstalk_host.h"
+#include "dstalk/dstalk_services.h"
+#include "../include/toml_parse.h"
+
+#include <string>
+#include <fstream>
+#include <sstream>
+
+// ============================================================
+// 全局状态 / Global state
+// ============================================================
+static const dstalk_host_api_t* g_host = nullptr;
+
+// ============================================================
+// 服务实现 / Service implementations
+//
+// W12.2: Eliminated private ConfigStore (was 90 lines duplicating core).
+// All get/set/load_file now delegate to the host store via g_host->config_get
+// and g_host->config_set, making the host store the single source of truth.
+// TOML parsing uses the shared dstalk::toml::parse() from toml_parse.h.
+// ============================================================
+
+// 从主机存储中按 key 获取配置值 / Retrieve a configuration value by key from the host store.
+static const char* config_get(const char* key) {
+    if (!g_host) return nullptr;
+    return g_host->config_get(key);
+}
+
+// 将键值对存入主机存储 / Store a configuration key-value pair into the host store.
+static int config_set(const char* key, const char* value) {
+    if (!g_host) return -1;
+    return g_host->config_set(key, value);
+}
+
+// 解析指定路径的 TOML 文件，将所有键值对加载到主机存储中 / Parse a TOML file at `path` and load all key-value pairs into the host store.
+static int config_load_file(const char* path) {
+    if (!g_host || !path) return -1;
+
+    std::ifstream file(path);
+    if (!file.is_open()) return -1;
+
+    std::stringstream ss;
+    ss << file.rdbuf();
+    std::string data = ss.str();
+
+    int count = 0;
+    dstalk::toml::parse(data, [&](const std::string& key, const std::string& value) {
+        g_host->config_set(key.c_str(), value.c_str());
+        ++count;
+    });
+
+    g_host->log(DSTALK_LOG_INFO,
+        "config: loaded %d entries from %s into host store", count, path);
+    return 0;
+}
+
+static dstalk_config_service_t g_service = {
+    config_get,
+    config_set,
+    config_load_file
+};
+
+// ============================================================
+// 插件生命周期 / Plugin lifecycle
+// ============================================================
+// 插件初始化：保存主机指针并注册 config 服务 vtable / Plugin init: store host pointer and register the config service vtable.
+static int on_init(const dstalk_host_api_t* host) {
+    g_host = host;
+
+    // W12.2: 该服务现为 host->config_get/set 的薄封装，建议直接调用主机 API / This service is now a thin wrapper around host->config_get/set.
+    // Direct host API calls are preferred.
+    host->log(DSTALK_LOG_INFO,
+        "plugin config service is deprecated, prefer host->config_get/set");
+
+    int rc = host->register_service("config", 1, &g_service);
+    if (rc != 0) {
+        host->log(DSTALK_LOG_WARN,
+            "config: register_service failed (rc=%d), service name may conflict", rc);
+    }
+    return (rc >= 0) ? 0 : -1;
+}
+
+// 插件关闭：无需清理本地存储（所有数据在主机存储中） / Plugin shutdown: no local store to clean up (all data lives in host store).
+static void on_shutdown() {
+    // W12.2: No local store to clean up — all data lives in host store.
+    // 无需清理本地存储——所有数据位于主机存储中。
+}
+
+static dstalk_plugin_info_t g_info = {
+    "config",              // name
+    "1.0.0",               // version
+    "Configuration service with TOML file support (deprecated: use host->config_get/set)",
+    DSTALK_API_VERSION,    // api_version
+    {nullptr},             // dependencies (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;
+}