An assistant rendering a temperature, a distance or a clock time was
guessing: the session instructions named only the trip currency, and nothing
could read what the user had picked.
The write works off an allow-list rather than off the settings row, because
that row also holds the webhook URL, the ntfy token and the Mapbox, Carto
and LLM keys, and getUserSettings hands some of those back in cleartext.
Everything outside the list is refused, including a key nobody has heard of
yet. The guard test asserts against the service's own encrypted and masked
sets rather than a copy of them, so a sixth key added there fails it.
Maurice