feat(fleet-prometheus): add piha/solaria/lustro node_exporter scrape targets

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/fleet-prometheus/prometheus.yml

@@ -26,14 +26,34 @@ scrape_configs:
     static_configs:
       - targets: ["localhost:9090"]
 
-  # First and only fleet target for this scaffold: the VPS-local node_exporter,
+  # Fleet node_exporters. One job, one static_configs entry per node, each
-  # which runs network_mode: host and listens on the host's :9100. Reached via
+  # carrying exactly one label: node:<name>. No availability/schedule/tier
-  # the host-gateway alias declared in docker-compose.yml.
+  # labels by design — "when to alert" (e.g. lustro/solaria are planned-off at
+  # times) is decided LATER by the brain from metric history (anomaly
+  # detection), never by static labels or time-based rules. Today's only goal
+  # is collecting metrics.
   - job_name: "fleet-node"
     static_configs:
+      # VPS-local node_exporter: network_mode: host on the host's :9100,
+      # reached via the host-gateway alias declared in docker-compose.yml.
       - targets: ["host.docker.internal:9100"]
         labels:
           node: "vps"
+      # Tailscale fleet targets — confirmed reachable from VPS (wget, 2026-06-26).
+      - targets: ["100.108.208.3:9100"]
+        labels:
+          node: "piha"
+      - targets: ["100.100.231.104:9100"]
+        labels:
+          node: "solaria"
+      - targets: ["100.99.85.73:9100"]
+        labels:
+          node: "lustro"
 
-  # NOTE: Tailscale fleet targets (100.x node_exporters across SATURN, SOLARIA,
+  # Deliberately NOT scraped (visible decision, not an oversight):
-  # PIHA, CHELSTY) are added in a separate step — not part of this scaffold.
+  #   - saturn (100.121.168.72): laptop/workstation, not infra; often powered
+  #     off → omitted.
+  #   - chelsty (100.122.201.22) + chelsty-infra (100.98.91.98): node_exporter
+  #     DOWN from VPS (LTE edge), 2026-06-26 — to be investigated separately
+  #     (exporter not deployed vs ACL block). Not listed as dead targets, which
+  #     would pollute future liveness signals.