Every minute the node that calculates metrics evaluates each enabled
x:Alert, read from the registry, with metric('name') or the underscore
name. An alert fires when its condition turns true: it emits
telemetry.alert-event with the rendered message, and queues one email per
recipient through the outbound queue, placeholders filled and
Auto-Submitted set. An alert naming an unknown metric is refused on save.
The shared alerts suite runs; every telemetry suite is un-gated.