issue: .md uploaded as application/octet-stream is sent to the extraction engine (Docling/Tika) instead of TextLoader

当 CONTENT_EXTRACTION_ENGINE 设为 docling 或 tika 时,以 application/octet-stream 上传的 .md / .markdown / .txt / .rst 文件会被送进 Docling/Tika 重新解析,而不是用 TextLoader








