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/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