sftpR - Robust SFTP Interface Using 'curl'

Provides a high-level, object-oriented interface for Secure File Transfer Protocol (SFTP) operations built upon the 'curl' package. The package implements an 'R6' class to manage persistent connections and provides 'tidyverse'-style functions for common file system tasks. Key features include recursive directory creation with idempotency support, "smart" local path resolution that distinguishes between files and directories, and the ability to download remote resources directly into memory as raw vectors for seamless integration into data processing pipelines. It is designed to handle common SFTP edge cases gracefully, providing informative error messages and robust path sanitization to ensure compatibility across different server configurations.