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/resources/values.yaml.jinja

@@ -0,0 +1,48 @@
+{# ---------------------------------------------------------------------------
+   Template for cluster/resources/{{ '<NNN>-<name>' if <domain>.<descriptor>_is_enabled }}/values.yaml.jinja
+
+   Standalone-chart shape. For services sharing one release via a `global` block,
+   use the shared-chart shape in references/helm-values.md §4 instead.
+
+   The macro wrapper and the four-line stripping footer are mandatory — they remove
+   blank lines left by unexpanded Jinja2 constructs, which would otherwise break the
+   rendered YAML.
+   --------------------------------------------------------------------------- #}
+{% macro render() %}
+# values for <NNN>-<name>
+replicaCount: {{ <domain>.get('<descriptor>', {}).get('replicas', 1) }}
+
+image:
+  repository: {{ <domain>.get('<descriptor>', {}).get('image', {}).get('address', '') }}
+  tag: {{ <domain>.get('<descriptor>', {}).get('image', {}).get('tag', '') }}
+  pullPolicy: Always
+
+imagePullSecrets:
+  - name: "storage-images"
+
+service:
+  type: ClusterIP
+  port: 80
+
+livenessProbe:
+  httpGet:
+    path: /health
+    port: <app-port>
+  periodSeconds: 60
+
+readinessProbe:
+  httpGet:
+    path: /health
+    port: <app-port>
+  periodSeconds: 60
+
+env:
+  targetPort: <app-port>
+  <env_var>: {{ <domain>.get('<descriptor>', {}).get('env', {}).get('<env_var>', '') }}
+{% endmacro %}
+{%- set result = render() -%}
+{%- for line in result.split('\n') -%}
+{% if line | trim | length != 0 -%}
+{{ line }}
+{% endif -%}
+{%- endfor %}