Add gitops-argo-cd agent skill

Consolidates the five cogarchhubgitops-* source skills into one skill with
scope routing: ArgoCD Applications, Copier templates, Helm values, environment
answer files, and the end-to-end resource-addition walkthrough.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

assets/example-cluster-resource/copier-variables.yaml

@@ -0,0 +1,46 @@
+# ---------------------------------------------------------------------------
+# Snippet to merge into copier.yaml when adding a new cluster resource.
+#
+# Replace:
+#   <domain>      existing domain object (operators, configuration, databases,
+#                 advantage_mcp, applications) — never add a top-level variable
+#   <descriptor>  this resource's key inside that domain
+#   <NNN>-<name>  the directory / ArgoCD Application name
+#
+# The flag name used here must be the one appearing in BOTH conditional directory
+# expressions (cluster/argocd/ and cluster/resources/).
+# ---------------------------------------------------------------------------
+
+<domain>:
+  <descriptor>_is_enabled:
+    type: bool
+    default: false
+    help: "Enable <NNN>-<name>"
+
+  <descriptor>:
+    image:
+      address:
+        type: str
+        default: ""
+        help: "Container image for <name>"
+      tag:
+        type: str
+        default: ""
+        help: "Container image tag for <name>"
+    replicas:
+      type: str
+      default: "1"
+      help: "Replica count for <name>"
+
+# ---------------------------------------------------------------------------
+# Matching snippet for <env>/copier-answers.yaml in each environment that should
+# run this resource. Feature flags are YAML booleans; Helm string-booleans such as
+# is_internal / maintenance are quoted strings — see references/environments.md §4.
+# ---------------------------------------------------------------------------
+#
+# <domain>:
+#   <descriptor>_is_enabled: true
+#   <descriptor>:
+#     image:
+#       address: <registry>/<image>
+#       tag: <version>