Not really solving all your cases, but I found tmux (or herdr) on a home server works pretty well. I just ssh into my home server and continue where I left off with the same claude/opencode open.

On a longer term, I think "assistant" style harnesses might help here, like vellum.ai. I no longer use that, but I asked it to create an ACP proxy through iroh (basically tailscale but on the application layer), and it managed to control claude on another device of mine. A friend did similar stuff with tailscale.

I have started writing a hobby harness with a web interface where I would like to support this "ACP proxy" mode natively, and also to make the models aware of different devices in some way and "move" work between them.