docs: describe the collector dashboard and its service-name lint

docs/swarm/services.md

@@ -207,7 +207,7 @@ kept.
 - `review-classifier`: review requests by outcome, the verdict mix, results per check, retried asks, and run duration p50 and p95.
 - `forge`: what the forge holds, and the forge process's CPU, memory and descriptors.
 - `gateway`: the gateway nginx on each hive's host: requests per second, connections by state, and accepted against handled connections.
-- `collector`: what the OTEL collectors accept, refuse, export and queue, with queue depth against capacity.
+- `collector`: what the hive and swarm OTEL collectors accept, refuse, export and queue, with queue depth against capacity.
 - `logstore`, `metricstore`: health of the log store and the metrics store.
 
 A new panel can read "No data" until its source exists: the push and commit
@@ -215,6 +215,17 @@ counters on `controller` appear after the first push webhook, the refused
 and failure series on `collector` appear once something fails, and the
 `review-classifier` panels fill as review requests arrive.
 
+**The `collector` dashboard.** It shows the self-metrics of the hive's
+collector and of the swarm's collector, which both carry the collector
+binary's default `service.name`, `otelcol-contrib`. The timeseries panels
+split by `server.port`: 8888 is the hive collector, 8889 the swarm
+collector. The per-container collectors (the secret store, NATS, Grafana,
+Authelia, the Victoria stores and the agents' forwarders) don't report
+their own metrics yet, so they have no lines here; the follow-up is
+tracked on the forge. `scripts/check-dashboard-service-names.sh` runs in CI
+and in `scripts/pre-push`. It fails when a dashboard query selects a
+`service.name` that nothing emits.
+
 **Where the data comes from.** The swarm's OTEL collector, below.
 
 The `controller` panels come from the controller itself. It exports OTLP