feat: add prometheus-adapter metrics component

config/components/prometheus-adapter/README.md

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+# Prometheus Adapter Resource Metrics
+
+Experimental `metrics.k8s.io` implementation backed by Prometheus Adapter.
+Enable only in clusters where Prometheus or VictoriaMetrics is the source of
+truth for Pod and Node CPU/memory usage.
+
+This component owns the cluster-wide `v1beta1.metrics.k8s.io` APIService when
+installed. Do not install it alongside another owner of the same APIService.
+
+The adapter expects Datum instance resource metrics with Kubernetes identity
+labels:
+
+- `datum_compute_instance_cpu_usage_seconds_total{namespace, pod, container, node}`
+- `datum_compute_instance_memory_working_set_bytes{namespace, pod, container, node}`
+
+Runtime-specific producers, such as Unikraft telemetry, should translate their
+local measurements into that shape before ingestion. The adapter then exposes
+those samples through the standard Kubernetes Resource Metrics API used by HPA.
+
+Infrastructure overlays must patch before enabling this component:
+
+- `PROMETHEUS_URL` should point at the local Prometheus or VictoriaMetrics query
+  endpoint.
+- `Certificate.spec.issuerRef` should point at the cluster's serving certificate
+  issuer. The default value is a placeholder `ClusterIssuer` named
+  `placeholder-issuer`.
+- The component defaults to `compute-system`. If an overlay deploys it in a
+  different namespace, patch the `Certificate.spec.dnsNames` and the
+  `APIService` service namespace / `cert-manager.io/inject-ca-from` annotation
+  in the consuming overlay.

config/components/prometheus-adapter/apiservice.yaml

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+apiVersion: apiregistration.k8s.io/v1
+kind: APIService
+metadata:
+  name: v1beta1.metrics.k8s.io
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+  annotations:
+    cert-manager.io/inject-ca-from: compute-system/compute-prometheus-adapter-serving-cert
+spec:
+  group: metrics.k8s.io
+  groupPriorityMinimum: 100
+  service:
+    name: compute-prometheus-adapter
+    namespace: compute-system
+    port: 443
+  version: v1beta1
+  versionPriority: 100

config/components/prometheus-adapter/config.yaml

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+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: compute-prometheus-adapter-config
+  namespace: compute-system
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+data:
+  config.yaml: |
+    resourceRules:
+      cpu:
+        containerQuery: |
+          sum by (<<.GroupBy>>) (
+            rate(datum_compute_instance_cpu_usage_seconds_total{<<.LabelMatchers>>,container!=""}[2m])
+          )
+        nodeQuery: |
+          sum by (<<.GroupBy>>) (
+            rate(datum_compute_instance_cpu_usage_seconds_total{<<.LabelMatchers>>}[2m])
+          )
+        resources:
+          overrides:
+            namespace:
+              resource: namespace
+            pod:
+              resource: pod
+            node:
+              resource: node
+        containerLabel: container
+      memory:
+        containerQuery: |
+          sum by (<<.GroupBy>>) (
+            datum_compute_instance_memory_working_set_bytes{<<.LabelMatchers>>,container!=""}
+          )
+        nodeQuery: |
+          sum by (<<.GroupBy>>) (
+            datum_compute_instance_memory_working_set_bytes{<<.LabelMatchers>>}
+          )
+        resources:
+          overrides:
+            namespace:
+              resource: namespace
+            pod:
+              resource: pod
+            node:
+              resource: node
+        containerLabel: container
+      window: 2m

config/components/prometheus-adapter/deployment.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: compute-prometheus-adapter
+  namespace: compute-system
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: compute-prometheus-adapter
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: compute-prometheus-adapter
+        app.kubernetes.io/part-of: compute
+    spec:
+      serviceAccountName: compute-prometheus-adapter
+      securityContext:
+        runAsNonRoot: true
+        runAsUser: 65532
+        runAsGroup: 65532
+        seccompProfile:
+          type: RuntimeDefault
+      containers:
+        - name: adapter
+          image: registry.k8s.io/prometheus-adapter/prometheus-adapter:v0.12.0
+          args:
+            - --secure-port=8443
+            - --tls-cert-file=/certs/tls.crt
+            - --tls-private-key-file=/certs/tls.key
+            - --prometheus-url=$(PROMETHEUS_URL)
+            - --config=/etc/adapter/config.yaml
+            - --metrics-relist-interval=1m
+            - --metrics-max-age=2m
+          env:
+            - name: PROMETHEUS_URL
+              value: http://prometheus-operated.monitoring.svc:9090
+          ports:
+            - containerPort: 8443
+              name: https
+              protocol: TCP
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop:
+                - ALL
+          livenessProbe:
+            httpGet:
+              path: /livez
+              port: 8443
+              scheme: HTTPS
+            initialDelaySeconds: 15
+            periodSeconds: 20
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: 8443
+              scheme: HTTPS
+            initialDelaySeconds: 5
+            periodSeconds: 10
+          resources:
+            limits:
+              cpu: 100m
+              memory: 128Mi
+            requests:
+              cpu: 10m
+              memory: 64Mi
+          volumeMounts:
+            - name: config
+              mountPath: /etc/adapter
+              readOnly: true
+            - name: serving-cert
+              mountPath: /certs
+              readOnly: true
+      volumes:
+        - name: config
+          configMap:
+            name: compute-prometheus-adapter-config
+        - name: serving-cert
+          secret:
+            secretName: compute-prometheus-adapter-serving-cert

config/components/prometheus-adapter/kustomization.yaml

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+apiVersion: kustomize.config.k8s.io/v1alpha1
+kind: Component
+
+resources:
+  - service_account.yaml
+  - rbac.yaml
+  - serving-cert.yaml
+  - config.yaml
+  - deployment.yaml
+  - service.yaml
+  - apiservice.yaml

config/components/prometheus-adapter/rbac.yaml

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+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: compute-prometheus-adapter-resource-reader
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+rules:
+  - apiGroups: [""]
+    resources: [nodes, pods, namespaces]
+    verbs: [get, list, watch]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: compute-prometheus-adapter-resource-reader
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: compute-prometheus-adapter-resource-reader
+subjects:
+  - kind: ServiceAccount
+    name: compute-prometheus-adapter
+    namespace: compute-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: compute-prometheus-adapter-auth-delegator
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: system:auth-delegator
+subjects:
+  - kind: ServiceAccount
+    name: compute-prometheus-adapter
+    namespace: compute-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: compute-prometheus-adapter-authentication-reader
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+rules:
+  - apiGroups: [""]
+    resources: [configmaps]
+    resourceNames: [extension-apiserver-authentication]
+    verbs: [get]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: compute-prometheus-adapter-authentication-reader
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: compute-prometheus-adapter-authentication-reader
+subjects:
+  - kind: ServiceAccount
+    name: compute-prometheus-adapter
+    namespace: compute-system

config/components/prometheus-adapter/service.yaml

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+apiVersion: v1
+kind: Service
+metadata:
+  name: compute-prometheus-adapter
+  namespace: compute-system
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+spec:
+  selector:
+    app.kubernetes.io/name: compute-prometheus-adapter
+  ports:
+    - name: https
+      port: 443
+      protocol: TCP
+      targetPort: https

config/components/prometheus-adapter/service_account.yaml

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+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: compute-prometheus-adapter
+  namespace: compute-system
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute

config/components/prometheus-adapter/serving-cert.yaml

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+apiVersion: cert-manager.io/v1
+kind: Certificate
+metadata:
+  name: compute-prometheus-adapter-serving-cert
+  namespace: compute-system
+  labels:
+    app.kubernetes.io/name: compute-prometheus-adapter
+    app.kubernetes.io/part-of: compute
+spec:
+  dnsNames:
+    - compute-prometheus-adapter.compute-system.svc
+    - compute-prometheus-adapter.compute-system.svc.cluster.local
+  issuerRef:
+    # Placeholder. Infra overlays must patch this issuer.
+    group: cert-manager.io
+    kind: ClusterIssuer
+    name: placeholder-issuer
+  secretName: compute-prometheus-adapter-serving-cert