feat: read YouTube cookies path from YOUTUBE_COOKIES_PATH environment variable

fix: append /no_thinking to all Qwen prompts to disable thinking mode via prompt

fix: explicitly disable thinking mode in Qwen InferenceClient calls for both answer and wiki query optimization

feat: use LangChain StrOutputParser for clean answer output; optimize Wikipedia search query with AI

use langchain

Add structured output with Pydantic, fix tool selection logic, add YouTube cookies support, disable thinking mode

structure code