hive-c0re's container-resource exporter has POSTed to a 404 for as long as
it has existed, silently: it passed the collector's base address to
`with_endpoint`, which the SDK takes verbatim, so every export went to `/`
instead of `/v1/metrics`. Nothing reported it — OTLP export failures go to
an error handler no binary here installs — so the daemon logged "exporter
enabled" and delivered nothing. VictoriaMetrics has never held a sample
under `service.name=hyperhive-c0re`.
Fix the way the rest of the repo already resolves an endpoint: an endpoint
option names a BASE, and the layer that knows the signal appends to it.
`hive-metric` — same SDK, same collector — never calls `with_endpoint`, and
`docs/observability.md` documents the append as system behaviour; the one
place a full path is spelled out is the VictoriaMetrics exporter, because
its far end is not a standard OTLP path.
So drop the call. The builder is now byte-identical to hive-metric's, and
hive-c0re's unit carries the standard `OTEL_EXPORTER_OTLP_ENDPOINT` for the
SDK to read. The address is bound once in nix and consumed twice, so what a
hive hands its agents and what it exports to itself cannot drift.
The enable signal moves to that same standard variable: "configured" and
"where it actually goes" become one string rather than two that agree by
convention. `HYPERHIVE_OTEL_*` keeps its own job, the agent-config
transport meta.rs reads — a name the SDK has never known, which is the bug.
The test changes shape with the fix. The old one asserted a URL this module
built; the new one pins that the exporter is gated on the variable the SDK
itself reads, because the fix is now an absence and an absence is what a
later "the endpoint is right there, just pass it" edit puts back.
Refs #3402
76f6b7c3b7