feat: 重构聊天服务以支持无状态设计和AI SDK集成

- 添加对AI SDK（@ai-sdk/*）的依赖支持
- 重构Agent和SubagentExecutor以支持无状态设计，systemPrompt通过ChatContext动态传入
- 移除旧版OpenAI/Anthropic/Gemini/Azure服务实现，统一使用VercelAIChatService
- 在ModelConfig中添加providerId字段以支持多提供商配置
- 添加自定义OpenAI兼容提供商支持
- 优化系统提示构建逻辑，支持按需构建和缓存控制
- 更新相关类型定义和测试用例
- 调整package.json依赖项以支持新功能

Author: echoVic

package.json

@@ -107,12 +107,19 @@
   },
   "dependencies": {
     "@agentclientprotocol/sdk": "^0.12.0",
+    "@ai-sdk/anthropic": "^3.0.7",
+    "@ai-sdk/azure": "^3.0.5",
+    "@ai-sdk/deepseek": "^2.0.4",
+    "@ai-sdk/google": "^3.0.4",
+    "@ai-sdk/openai": "^3.0.5",
+    "@ai-sdk/openai-compatible": "^2.0.4",
     "@anthropic-ai/sdk": "^0.71.2",
     "@azure/identity": "^4.13.0",
     "@google/genai": "^1.34.0",
     "@inkjs/ui": "^2.0.0",
     "@modelcontextprotocol/sdk": "^1.17.4",
     "ahooks": "^3.9.5",
+    "ai": "^6.0.39",
     "ansi-escapes": "^7.2.0",
     "async-mutex": "^0.5.0",
     "axios": "^1.12.2",