docs(agents): record the compose-only observability gap found by the reboot

Rebooting Dankclaw for the amd_iommu=off change exposed five services that
exist only as compose.yaml services with no Quadlet unit (prometheus, grafana,
loki, alloy, node-exporter): they did not come back and had to be restored by
hand. The boot-persistence rule already requires units for them; this records
the concrete gap so the next reboot is not a surprise.

AGENTS.md

@@ -200,6 +200,16 @@ Pi-hole unit existed but crash-looped on a sysctl conflict (a later-sorted
 drop-in reset `net.ipv4.ip_unprivileged_port_start` to 80), taking LAN DNS
 down with it.
 
+**Known gap (2026-09-11, found while rebooting Dankclaw for the `amd_iommu=off`
+change):** five Dankclaw services still run only from `dankclaw/compose.yaml`
+with no Quadlet unit — `prometheus`, `grafana`, `loki`, `alloy` and
+`node-exporter` (all under `~/.config/containers/systemd/` absent, but present
+in the compose file). They did not come back after that reboot and were
+restored with `./scripts/deploy.sh dankclaw --service <name>`; they will not
+survive the next one either. Giving them units is tracked work, not a solved
+problem — treat every reboot as expected to take the observability stack down
+until it is done.
+
 ## Testing
 
 Tests are mandatory before commit. `bats` must be installed on the