Pushes synthetic cairnobs.metrics/cairnobs.heartbeat-tagged records
straight to ingest so a demo deployment's Hosts page and per-host detail
page have CPU/memory/disk to show. Neither benchmark-fixture nor
windows-fixture emits those two attributes -- only the real agent does
-- so nothing else could populate that page.
Superseded by /hack/demo-simulator in the next commit, which covers the
same records as part of a whole fleet; kept because it is still the
smallest thing that fills the Hosts page on its own.
