main: 增强工具调用与消息流程

- 支持 tool.call 和 tool.result 消息类型处理
- 引入 Tool 调度与执行逻辑，支持超时与结果截断
- 增加 ToolRegistry 和 ToolExecutor 管理工具定义与执行
- 更新上下文构建与消息映射逻辑，适配工具闭环处理
- 扩展配置与环境变量，支持 Tool 调用相关选项
- 增强单元测试覆盖工具调用与执行情景
- 更新文档和 OpenAPI，新增工具相关说明与模型定义

app/Services/ContextBuilder.php

@@ -19,13 +19,14 @@ class ContextBuilder
         return new AgentContext(
             $runId,
             $sessionId,
-            'You are an agent inside ARS. Respond concisely in plain text.',
+            'You are an agent inside ARS. Respond concisely in markdown format. Use the following conversation context.',
             $messages->map(function (Message $message) {
                 return [
                     'message_id' => $message->message_id,
                     'role' => $message->role,
                     'type' => $message->type,
                     'content' => $message->content,
+                    'payload' => $message->payload,
                     'seq' => $message->seq,
                 ];
             })->values()->all()
@@ -36,8 +37,8 @@ class ContextBuilder
     {
         return Message::query()
             ->where('session_id', $sessionId)
-            ->whereIn('role', [Message::ROLE_USER, Message::ROLE_AGENT])
-            ->whereIn('type', ['user.prompt', 'agent.message'])
+            ->whereIn('role', [Message::ROLE_USER, Message::ROLE_AGENT, Message::ROLE_TOOL])
+            ->whereIn('type', ['user.prompt', 'agent.message', 'tool.call', 'tool.result'])
             ->orderByDesc('seq')
             ->limit($this->limit)
             ->get()