feat(github-runner): add top Linux repo runners

apps/monitoring/noc-monitoring.yaml

@@ -974,6 +974,19 @@ data:
               summary: "Deployment {{ $labels.namespace }}/{{ $labels.deployment }} replica mismatch"
               description: "Spec wants {{ $labels.spec_replicas }} but only {{ $value }} available. Likely a rollout stuck on probe failure, scheduling, or PVC."
 
+          - alert: LinuxRunnerOffline
+            expr: |
+              kube_deployment_status_replicas_available{namespace="github-runner",deployment=~"github-runner(|-(puppet|signage|dms|telephony|print-web|chat|mysql|kiosk-linux))"} < 1
+            for: 10m
+            labels:
+              severity: warning
+              service: github-runner
+              alert_channel: thermal_print
+            annotations:
+              summary: "Linux GitHub Actions runner offline: {{ $labels.deployment }}"
+              description: "{{ $labels.deployment }} has no available runner pod for 10 minutes. GitHub jobs using [self-hosted, linux, fc-build-linux] for its repo will queue at $0 until the runner returns."
+              runbook_url: "https://gitea.iamworkin.lan/bluejay/FlowerCore.Notes/src/branch/master/docs/infrastructure/self-hosted-runner-fleet.md"
+
           # Q-MR-3 (2026-05-11): multus memory pressure — catches the next OOM
           # cascade BEFORE multus is OOM-killed cluster-wide. The 2026-05-10
           # outage (21h) hit because no alert fired on the rising multus working
@@ -3427,6 +3440,33 @@ data:
                 relativeTimeRange: {from: 120, to: 0}
                 datasourceUid: __expr__
                 model: {type: threshold, expression: B, conditions: [{evaluator: {params: [1], type: lt}}], refId: C}
+          - uid: linux-runner-offline
+            title: LinuxRunnerOffline
+            condition: C
+            for: 10m
+            noDataState: Alerting
+            execErrState: OK
+            annotations:
+              summary: Linux GitHub Actions runner offline
+              description: "A repo-scoped fc-build-linux runner deployment has no available pod. Jobs will queue at $0 until ArgoCD/K8s returns the runner."
+              runbook_url: "https://gitea.iamworkin.lan/bluejay/FlowerCore.Notes/src/branch/master/docs/infrastructure/self-hosted-runner-fleet.md"
+            labels:
+              severity: warning
+              service: github-runner
+              alert_channel: thermal_print
+            data:
+              - refId: A
+                relativeTimeRange: {from: 600, to: 0}
+                datasourceUid: prometheus
+                model: {expr: 'min by(deployment) (kube_deployment_status_replicas_available{namespace="github-runner",deployment=~"github-runner(|-(puppet|signage|dms|telephony|print-web|chat|mysql|kiosk-linux))"})', instant: true, refId: A}
+              - refId: B
+                relativeTimeRange: {from: 600, to: 0}
+                datasourceUid: __expr__
+                model: {type: reduce, expression: A, reducer: last, refId: B}
+              - refId: C
+                relativeTimeRange: {from: 600, to: 0}
+                datasourceUid: __expr__
+                model: {type: threshold, expression: B, conditions: [{evaluator: {params: [1], type: lt}}], refId: C}
           - uid: high-cpu
             title: High CPU (>85%)
             condition: C