The manager is the ONLY thing that talks to InfluxDB, both directions; hosts hold
no token and never reach it.
- influx.go: influxSink implements MetricsSink — each agent HealthSnapshot is
written as a fleet_health point, identity (serial/hostnqn/starship) as TAGS
from the AUTHENTICATED stream (a host can only write its own series), telemetry
as fields. QueryField answers the SPA's read: a Flux query built with a strict
FIELD WHITELIST + hex-serial guard + parsed-duration range, so no caller input
is interpolated raw (injection-safe). Server-side influxdb-client-go/v2.
- admin.go: GET /api/hosts/{serial}/metrics?field=&range= -> time-series JSON;
503 when InfluxDB isn't wired, 400 on a bad range, 404 for unknown host.
- main.go: sink created when FLEET_MGR_INFLUX_URL+_TOKEN set, fed to the agent
hub; nil -> no-op sink so the manager runs without metrics.
Tests: snapshotPoint tags/fields/time, fluxQuery contents + %q quoting, and
QueryField rejects a non-hex serial + non-whitelisted field. build/test/vet/gofmt
clean. Live InfluxDB path validated in the compose bench (ckpt 6).
