Support forced web search and URL context features

[bbbugg]

• 仿照强制思考，添加强制联网搜索和网址上下文功能，支持openai兼容接口和gemini原生接口
• 添加强制思考、强制联网搜索、强制网址上下文的环境变量，默认为false。
  • this.forceThinking = process.env.FORCE_THINKING === "true";
this.forceWebSearch = process.env.FORCE_WEB_SEARCH === "true";
this.forceUrlContext = process.env.FORCE_URL_CONTEXT === "true";