fix(cli): surface chat history HTTP errors (#476)

rig chatroom history and rig chatroom wait now surface HTTP errors from the chat history API instead of hiding them.

- history: with --json, the body is printed as before and the exit code is 1. In plain mode, the error (or "Failed (HTTP n)") goes to stderr and the exit code is 1, instead of "No messages." with exit 0.
- wait: the first HTTP error is reported and the command exits 1, instead of polling until the timeout.
- Successful output is unchanged.