asciinema/asciinema ? reverse-engineered prompt

Build me a command line app that can record terminal sessions and save them as lightweight cast files, then replay them later inside the terminal. I want it to feel like a real terminal recorder, not a screen video tool, so it should capture what happens in the shell, support optional keyboard input capture, and save metadata like terminal size and command details.

It should also be able to stream a live terminal session to other viewers, both through a local web server for watching on the same network and through a remote relay if needed. Please include playback controls like speed changes, looping, pause and resume, stepping through the session, and markers. It would be great if it can convert recordings between formats, join multiple recordings together, and read from local files or URLs.

Make it work well on Linux, macOS, and FreeBSD, and include sensible config file support plus shell completions and man pages if that fits the project. Look up current docs online if you need to.