Host metrics arrived carrying `hive` and no host attribute, so "which
host is out of memory" was answerable only as "which hive" -- true only
while a hive is one machine, which is the framing the swarm work exists
to end.
Adds the collector's own `resourcedetection` processor to the metrics
pipeline, emitting both `host.name` and `host.id`.
`resourcedetection` rather than a value picked in nix: this is the
canonical OTel mechanism for host identity, and choosing our own would
answer a question the tool already answers, differently from every other
deployment. A resource attribute is captured into the stored series, so
a private naming scheme is expensive in the way that lasts.
Both attributes, deliberately: `host.name` is readable and what a panel
groups by, but splits the series silently on a rename with nothing
linking old to new; `host.id` survives that and is unreadable alone.
Hosts get renamed and repurposed exactly when services move off one box.
The processor sits in the pipeline, so it applies to every receiver --
agent-pushed OTLP and scraped targets included, not just `hostmetrics`.
Keys verified against otelcol-contrib 0.151.0 with two deliberate
mutations rejected in the same run (a bogus resource attribute and a
bogus detector key), so "accepted" is distinguishable from a validator
that ignores what it does not recognise.
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