Add docs/observability.md covering all services.hyperhive.otel.*
options: enable, endpoint, protocol, headersCredential,
extraResourceAttributes, debug (new in cb0a66147a), and
metricIntervalMs.
Includes:
- Built-in OTEL_RESOURCE_ATTRIBUTES labels (service.name, agent, hive, swarm)
- Cumulative temporality note (avoids Prometheus DELTA drop)
- Network note for host-side collectors on non-standard ports,
cross-referencing docs/network.md exposeHostPorts
Also:
- CLAUDE.md: add reading-path entry for the new doc
- docs/network.md: link the OTEL mention to observability.md
Closes no issue — gap found during doc sweep.
