remove otel.metricIntervalMs and the host-level otel.debug

Both are ignored with a warning through the same shim, now
nix/host-modules/hive-options-removed.nix.

- otel.metricIntervalMs: claude in every agent and hive-c0re's
  container-resource exporter run at the 60s default. The agent-level
  services.hyperhive.agent.otel.metricIntervalMs, set only by the meta
  render, goes too (warning shim in nix/agent-modules/otel-removed.nix).
- otel.debug: services.hyperhive.agent.otel.debug stays, documented and
  set in an agent's own config; the meta render no longer emits it.

docs/scheduler/observability.md

@@ -325,7 +325,7 @@ labels (`hive`, `swarm`, …) ride on the resource via
 
 <!-- vale write-good.Passive = NO -->
 
-Cadence follows `metricIntervalMs` (default 60s). Transport is OTLP/HTTP
+The export cadence is a fixed 60s. Transport is OTLP/HTTP
 (JSON) to the hive collector's bridge address, with no auth header — that
 first hop is unauthenticated for every producer on this host, and the upstream
 credential stays on the swarm tier.
@@ -409,8 +409,8 @@ window used by agent** panel (health tab) divides one by the other.
 Resource attributes (`service.name`, `agent`, `swarm`) come from the
 same container-wide `OTEL_RESOURCE_ATTRIBUTES` as everything else in this
 section, and the swarm's collector adds `hive` — nothing extra to configure.
-Cadence follows `HYPERHIVE_OTEL_METRIC_INTERVAL_MS` (default 60s, same variable + default as
-`hive-c0re`'s container-resource export above) — that only controls how often
+Cadence follows `HYPERHIVE_OTEL_METRIC_INTERVAL_MS` (default 60s, the same
+cadence as `hive-c0re`'s container-resource export above). That only controls how often
 the harness flushes the batched points to the collector, not how often it
 records them (every turn, always).