prompt should support multiple values

`prompt` in the authentication options to support space-delimited, case-sensitive list of string values.
For example, `prompt: "select_account login"` will ask the end-user to select an account and then authenticate.

No file or test is named in the issue. Start by locating the authentication-options handling for prompt and its existing tests, then trace how prompt values are parsed and passed through. Done means accepting a space-delimited, case-sensitive list such as "select_account login" and covering that behavior with tests.

Written by the indexing model from the issue text.