docs(observability): correct current state and log-pipeline root cause

AGENTS.md: the rule set is now two groups (llm-fleet + vllm-fleet) and a
Loki datasource is provisioned beside Prometheus.
Observability.md: current-state census refreshed (three LLM targets up,
two rule groups, Loki datasource); logs still carry no data.
Alloy.md: replace the 'wrong glob' theory with the proven cause - a
rootless container cannot read the 0640 systemd-journal files (a rootless
busybox read returns DENIED), and rootless quadlet logs land in the user
journal the system-only source never reads. Closing it is a
permission/architecture decision, not a config glob.

AGENTS.md

@@ -166,9 +166,11 @@ bare compose container never returned; 2026-09-11: five observability
 services had no units). The observability services now have units under
 `dankclaw/observability/quadlet/` and their compose definitions were removed —
 one owner per container name. The stack is **configured and delivering as of
-2026-09-17**: a Grafana datasource and the `llm-fleet` dashboard are
-provisioned from `shared/grafana/provisioning/`, `shared/prometheus/rules/
-llm-fleet.yml` loads 5 alert rules + 1 recording rule, and firing rules are
+2026-09-17**: Grafana datasources (Prometheus and Loki) and the `llm-fleet`
+dashboard are provisioned from `shared/grafana/provisioning/`, and
+`shared/prometheus/rules/llm-fleet.yml` loads two rule groups — `llm-fleet`
+(llama.cpp/halogen, `llamacpp:*`) and `vllm-fleet` (radiance, `vllm:*`) — alert
++ recording rules, and firing rules are
 delivered: Prometheus → Alertmanager (`dankclaw/observability/quadlet/
 alertmanager.container`, loopback :9093) → host-side Signal relay
 (`scripts/signal-relay.py`, user unit, 192.168.0.143:18093 — the host LAN