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.

nix/host-modules/hive-c0re/environment.nix

@@ -125,12 +125,6 @@ in
   # The rule: the collector holding the credential achieves nothing while
   # anything else hands out a copy, so there is exactly one holder and it
   # is on the host.
-  // lib.optionalAttrs (otel.metricIntervalMs != null) {
-    HYPERHIVE_OTEL_METRIC_INTERVAL_MS = toString otel.metricIntervalMs;
-  }
-  // lib.optionalAttrs otel.debug {
-    HYPERHIVE_OTEL_DEBUG = "1";
-  }
 )
 // {
   # In-cluster forge URL — the gateway vhost (`forge.<domain>`), which