feat(cloud): add jcode cloud sessions configure/status for Jade API defaults

Persist Jade API base, bearer token, token id, default user id, and
helper path in ~/.jcode/cloud_sessions.json (0600), injected as
JADE_API_* env for the private helper so secrets stay off the CLI and
out of shell history. --api-token-env reads (and validates non-empty)
the token from an env var; status/JSON never print the token value.