deploy: add node-exporter DaemonSet + vmagent scrape job

Per-node host metrics (node_filesystem_*, node_memory_*, node_load*) were
missing — a node running out of disk would silently fail the cluster before
any dashboard signal (RUNBOOK §11.1 gap #9). Adds:
- node-exporter DaemonSet (pod-networked, :9100; host /proc,/sys,/ ro) so
  vmagent scrapes it pod-to-pod over the cluster CIDR, independent of node
  public IPs (the netpol node-IP list is OVH-stale).
- two additive NetworkPolicies (default-deny-all is in force): ingress to
  node-exporter from vmagent, and vmagent egress to the pod CIDR on :9100.
- a node-exporter scrape job in the vmagent-config ConfigMap.

Feeds the new "Node host health" row (disk/mem/load) on the eli5 dashboard.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

deploy-k3s/manifests/observability/node-exporter.yaml

@@ -0,0 +1,126 @@
+# node-exporter — per-node host metrics (filesystem, memory, load, CPU).
+# Runs as a normal pod (NOT hostNetwork) so vmagent scrapes it pod-to-pod over
+# the cluster CIDR, avoiding any dependency on node public IPs (the netpol
+# node-IP list is OVH-stale). Host /proc, /sys and / are bind-mounted read-only
+# so the filesystem/memory/load collectors read the real host, not the pod ns.
+# Added 2026-06-08 to close RUNBOOK §11.1 gap #9 (node disk/mem were unmonitored).
+apiVersion: apps/v1
+kind: DaemonSet
+metadata:
+  name: node-exporter
+  namespace: honeydue
+  labels:
+    app.kubernetes.io/name: node-exporter
+    app.kubernetes.io/part-of: honeydue
+spec:
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: node-exporter
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: node-exporter
+        app.kubernetes.io/part-of: honeydue
+    spec:
+      # Run on every node, including any tainted control-plane nodes.
+      tolerations:
+        - operator: Exists
+      securityContext:
+        runAsNonRoot: true
+        runAsUser: 65534
+        seccompProfile:
+          type: RuntimeDefault
+      containers:
+        - name: node-exporter
+          image: quay.io/prometheus/node-exporter:v1.8.2  # TODO digest-pin (audit K3S-F14)
+          imagePullPolicy: IfNotPresent
+          args:
+            - --path.procfs=/host/proc
+            - --path.sysfs=/host/sys
+            - --path.rootfs=/host/root
+            # Only report real host mounts; drop the kubelet/container churn.
+            - --collector.filesystem.mount-points-exclude=^/(dev|proc|sys|run|var/lib/kubelet/.+|var/lib/docker/.+|var/lib/containerd/.+)($|/)
+            - --collector.filesystem.fs-types-exclude=^(autofs|binfmt_misc|bpf|cgroup2?|configfs|debugfs|devpts|devtmpfs|fusectl|hugetlbfs|iso9660|mqueue|nsfs|overlay|proc|procfs|pstore|rpc_pipefs|securityfs|selinuxfs|squashfs|sysfs|tracefs)$
+            - --no-collector.wifi
+            - --no-collector.hwmon
+            - --web.listen-address=:9100
+          ports:
+            - name: metrics
+              containerPort: 9100
+              protocol: TCP
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop: ["ALL"]
+          resources:
+            requests:
+              cpu: 30m
+              memory: 32Mi
+            limits:
+              cpu: 200m
+              memory: 128Mi
+          volumeMounts:
+            - name: proc
+              mountPath: /host/proc
+              readOnly: true
+            - name: sys
+              mountPath: /host/sys
+              readOnly: true
+            - name: root
+              mountPath: /host/root
+              mountPropagation: HostToContainer
+              readOnly: true
+      volumes:
+        - name: proc
+          hostPath:
+            path: /proc
+        - name: sys
+          hostPath:
+            path: /sys
+        - name: root
+          hostPath:
+            path: /
+---
+# default-deny-all blocks ingress; allow vmagent to scrape :9100.
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: allow-ingress-to-node-exporter
+  namespace: honeydue
+spec:
+  podSelector:
+    matchLabels:
+      app.kubernetes.io/name: node-exporter
+  policyTypes:
+    - Ingress
+  ingress:
+    - from:
+        - podSelector:
+            matchLabels:
+              app.kubernetes.io/name: vmagent
+      ports:
+        - port: 9100
+          protocol: TCP
+---
+# vmagent's existing egress policy only opens :8000/:8080 to the pod CIDR.
+# Additive policy (NetworkPolicies are OR'd) opening :9100 for the node-exporter
+# scrape — leaves the working allow-egress-from-vmagent policy untouched.
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: allow-egress-from-vmagent-to-node-exporter
+  namespace: honeydue
+spec:
+  podSelector:
+    matchLabels:
+      app.kubernetes.io/name: vmagent
+  policyTypes:
+    - Egress
+  egress:
+    - to:
+        - ipBlock:
+            cidr: 10.42.0.0/16
+      ports:
+        - port: 9100
+          protocol: TCP