This is awesome! I hate the way tmux hijacks so much of my terminal's behavior (scrollback, seaching with escape-/, etc.) and I've been looking for something like this that will manage persistent sessions without any extra nonsense.
BTW I think your readme shouldn't just characterize it as a resumeable ssh tool. I often need to start a long running process that I want to reconnect to later, or I want to put some always-on system service inside a tmux container so I can easily jump in and see logs or mess with things in one way or another. There's a lot of utility besides just handling network dropouts.
I once had a VPN utility that HAD to be closed with a Keyboard Interrupt in order for it to shut-off properly, so my systemd setup for it didn’t work. I ended up making bash aliases for tmux commands to run it and send the keyboard interrupt signal into it to stop it. I’m sure there was a way to do this with systemd, but tmux was easy, if a bit jank.
In Python, I sometimes try data-oriented programming, using lists and dicts to structure data. And I find that it does not work well. Once I get two or more levels of nesting, I find it far too easy to get confused about which level I'm on, which is not helped by Python's lack of strong typing. In these situations, I often introduce objects that wrap the map or dict, and have methods that make sense for that level. In other words, the objects can be viewed as providing clear documentation for the whole nested structure, and how it can be navigated.
Mypy for example can also see the types of the dictionary are supposed to be when you use it just like a normal dictionary.