- Added sftp-types.ts to define SFTP protocol constants, types, and attributes.
- Introduced sftp.ts to implement the SFTP client, handling requests, responses, and error management.
- Implemented methods for file operations including open, read, write, remove, and directory management.
- Added error handling for SFTP protocol errors and timeouts.
- Included utility functions for encoding and decoding SFTP packets.
cmliu