kb-retriever 是做什么的？
A retrieval and Q&A assistant for local knowledge base directories. Core process: (1) hierarchical index navigation, (2) when encountering PDF/Excel files, must first read references to learn the processing method, (3) process files then retrieve. Uses grep, Read, pdfplumber, and pandas in combination based on file type for progressive retrieval to avoid loading entire files. Use this skill when the user's question involves "answering questions from a knowledge base directory / retrieving information / looking up materials."