a failed tea-login oneshot used to abort `nixos-container update`
(switch-to-configuration exits 4), which blocked every rebuild
whether the agent needed tea or not. drop `set -e`, exit 0 on
every failure path (mkdir, tea login add, missing forge). also fix
the unit description, which hardcoded /state (manager-only) — sub-
agents have /agents/<name>/state.
6652ae90ab