pic admins create/set --password and pic login --token accepted secrets
on argv, where they leak into shell history, ps aux, and
/proc/<pid>/cmdline. Now only --password -/--token - (stdin) is allowed;
an inline value is rejected with guidance. PICLOUD_TOKEN env still covers
CI for login.
Also (M2): the interactive admins password prompt used read_line, which
echoes despite a 'no echo' claim — switched to rpassword::prompt_password
(already a dep via login). Removed the now-dead ReadLine trait + Write
import.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>