Name and order the ChatGPT login code

Every package-level name of the ChatGPT login starts with chatgpt, and
its file is chatgpt.go. The login has an issuer, a client ID, a token
file, and a poll interval, and the prefix keeps these names apart from
the names of the Telegram bot and the model client. The client ID
constant does not name another program.

The declarations of the login files follow the order of the go-code
skill. The behavior does not change.

Issue: 947bddb