Add kubernetes-deployment: probes, shutdown, JVM ergonomics, HPA

Companion code for "Deploying Spring Boot 4 on Kubernetes: Probes, Graceful
Shutdown, Limits and JVM Ergonomics". A dependency outage under three
probe-group setups, a rolling restart under load four ways (three runs
each), the JVM's ergonomic choices for nine pod shapes, one GC-heavy load
under five CPU limits with throttling counters, and an HPA driven by a
Micrometer gauge through prometheus-adapter. Measured on k3s v1.36.4.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01C3TETMrqVUWeFkNtz3Jbo3

kubernetes-deployment/k8s/gc-lab.yaml

@@ -0,0 +1,38 @@
+# One replica used only by the CPU-limit / GC experiment. scripts/demo-gc-throttling.sh patches
+# resources and JAVA_TOOL_OPTIONS per variant.
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: gc-lab
+  namespace: demo
+spec:
+  replicas: 1
+  selector:
+    matchLabels: {app: gc-lab}
+  template:
+    metadata:
+      labels: {app: gc-lab}
+    spec:
+      containers:
+        - name: app
+          image: sbd/k8s-demo:1
+          imagePullPolicy: Never
+          ports: [{name: http, containerPort: 8080}]
+          env:
+            - name: JAVA_TOOL_OPTIONS
+              value: ""
+          resources:
+            requests: {cpu: 100m, memory: 256Mi}
+            limits: {cpu: "1", memory: 1Gi}
+          readinessProbe:
+            httpGet: {path: /actuator/health/readiness, port: http}
+            periodSeconds: 2
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: gc-lab
+  namespace: demo
+spec:
+  selector: {app: gc-lab}
+  ports: [{name: http, port: 8080, targetPort: http}]