Import minecraft-server chart for Fleet migration stage 1 (java8 line)

Imports the chart from cluster-config functionally unchanged, wires it into
the publish/validate/install-test pipelines and publishes it as the first of
three Java lines (0.4.0+upjava8).

The only deviation from the source chart is the chart-global scaleDown flag
plus a server.replicas value, following the satisfactory pattern: two of the
three servers stand at 0 replicas in the cluster, which the chart could not
express, and Fleet would otherwise start them on reconcile. The default
(scaleDown: false) still renders replicas: 1, so the rendering of the running
server is unchanged - verified byte-identical against the three real values
files for all three Java lines.

Known deficiencies (hardening, probes, naming scheme, hardcoded values,
missing icon, the misleading mc-router auto-discovery annotations) are left
untouched on purpose and are scheduled for stage 2.

ci/minecraft-server/fixtures.yaml

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+# Fixtures for the minecraft-server install-test (release name: ci).
+#
+# The chart hardcodes storageClassName "longhorn" in its PVC, which does not
+# exist in k3d: a no-provisioner StorageClass named "longhorn" plus a pre-bound
+# hostPath PV stand in for it. A node-setup Job pre-creates the hostPath
+# directory world-writable, because the image's entrypoint chowns /data to
+# uid 1000 and hostPath volumes do not support fsGroup.
+#
+# The Secret is what the 1Password operator would otherwise materialize from
+# the OnePasswordItem CR the chart renders (stub CRD in ci/common/).
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: longhorn
+provisioner: kubernetes.io/no-provisioner
+---
+apiVersion: batch/v1
+kind: Job
+metadata:
+  name: node-setup
+spec:
+  backoffLimit: 2
+  template:
+    spec:
+      restartPolicy: Never
+      containers:
+        - name: setup
+          image: public.ecr.aws/docker/library/busybox:1.36
+          command:
+            - sh
+            - -c
+            - >
+              mkdir -p /pv/minecraft-server/mc-data /pv/minecraft-server/mc-modpacks &&
+              chmod -R 0777 /pv/minecraft-server
+          volumeMounts:
+            - name: pv
+              mountPath: /pv
+      volumes:
+        - name: pv
+          hostPath:
+            path: /var/lib/ci-pv
+            type: DirectoryOrCreate
+---
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: ci-minecraft-server-data
+spec:
+  capacity:
+    storage: 5Gi
+  accessModes:
+    - ReadWriteOnce
+  persistentVolumeReclaimPolicy: Retain
+  storageClassName: longhorn
+  claimRef:
+    namespace: default
+    name: ci-mc-volume-claim
+  hostPath:
+    path: /var/lib/ci-pv/minecraft-server
+    type: DirectoryOrCreate
+---
+apiVersion: v1
+kind: Secret
+metadata:
+  name: ci-mc-secret
+stringData:
+  rcon-password: ci-dummy-rcon-password
+  # Only consumed when curseforge.enabled is true; provided so the CI install
+  # keeps working if the test values ever enable a CurseForge modpack.
+  curseforge-api-key: ci-dummy-curseforge-key

ci/minecraft-server/settings.env

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+# The itzg/minecraft-server image is large and the server downloads its vanilla
+# server jar on first start before the container settles.
+INSTALL_TIMEOUT=600

ci/minecraft-server/test-values.yaml

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+# Values for the minecraft-server install-test. Kept as close to the real
+# deployments as possible; only what a CI runner cannot provide is overridden.
+#
+# 1. minecraft.version: the image tag comes from .Chart.AppVersion, so the JVM
+#    in the image is fixed per published chart version and the Minecraft
+#    version has to match that Java line - Java 8 runs Minecraft up to 1.16.5,
+#    modern versions need Java 17/21 and refuse to start otherwise. This chart
+#    version publishes appVersion "java8", hence 1.12.2 (a classic Java 8 era
+#    release). This value is bumped together with appVersion in the java17 and
+#    java21 follow-up PRs.
+#    The production default is "LATEST", which would pull a 1.21.x server that
+#    a Java 8 JVM cannot load at all.
+# 2. minecraft.resources.storage: the production 32Gi world volume is backed by
+#    a static hostPath PV in CI (see fixtures.yaml); 2Gi is plenty for a server
+#    that only has to boot.
+# 3. minecraft.resources.memory: sets the JVM heap (-Xmx); 1G instead of 4G
+#    keeps the runner comfortable. The container resource *requests* are
+#    hardcoded in the template (cpu 2 / memory 4Gi) and cannot be overridden -
+#    they fit a 4-vCPU/16GB GitHub runner, and making them configurable is part
+#    of the stage-2 convention alignment.
+# 4. server.outwardPort stays at the chart default 30565: unlike minecraft-router
+#    that default is already inside the Kubernetes node-port range
+#    (30000-32767), so the k3d API server accepts it unchanged.
+secrets:
+  minecraftServerRef: vaults/CI/items/minecraft-server
+
+minecraft:
+  version: "1.12.2"
+  management:
+    # opPlayers deliberately stays at the default (null): the image resolves
+    # every name in OPS against the external Playerdb API and aborts the whole
+    # startup when a name does not resolve, so any placeholder name would break
+    # the install-test and a real name would make CI depend on a third-party
+    # lookup.
+    maxPlayers: 2
+  resources:
+    storage: 2Gi
+    memory: "1"