"context" is just JSONL files on your machine. afaik these are not in any way bound to a subscription, so you'd just need to logout, login to the new account, and run /resume

All context is stored in the repository. I start each task with empty context (/clear). I consider this to be the equivalent of "reproducible builds" for coding agents.

Use a layer on top of it like T3 Code that can handle this for you