File Transfer Speed and Progress Display Enhancement While Upload/Download

I really enjoy using rz/sz for file transfers and I'm really looking forward to having progress display during the file transfer process.

Real-time Speed Display:
Implement a feature that displays the current transfer speed in a prominent and easily understandable format. The speed should be updated dynamically as the transfer progresses, allowing users to monitor the efficiency of the transfer process.

Progress Indicator:
Integrate a progress bar or similar visual representation to illustrate the advancement of the file transfer. The progress indicator should reflect the percentage of completion and update smoothly throughout the process.

Start by locating the rz/sz file-transfer handling and the terminal UI responsible for displaying transfer status. Define how current speed, percentage completion, and a progress indicator should appear and update during uploads and downloads. Done means both transfer directions show all requested status information during a real transfer.

Written by the indexing model from the issue text.