Add cluster-side connect operations to the ArgoCD skill

Fold the operational half of ArgoCD work into this skill, which until now
covered only authoring the Copier-templated repo. The two never overlapped:
authoring edits files in git, connecting applies objects to a cluster.

- Add references/connecting-a-repo.md: host-key trust, repository Secret
  registration with its project-scoping decision table, bootstrap apply
  ordering, SSO RBAC, prerequisites, and verification commands.
- Add references/connect-env-vars.md: layered .env loading, variable table,
  CLI flags, and SSH deploy-key rules.
- Add SKILL.md section 11 plus scope-routing rows, and state the split:
  sections 1-10 author, section 11 operates.
- Map the numbered cluster/0000-bootstrap layout onto the cluster/argocd
  layout, since the connect scripts reference those folder names directly.

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

README.md

@@ -20,6 +20,8 @@ development-gitops-argo-cd/
 │   ├── helm-values.md                        # values.yaml.jinja, images, global block, probes
 │   ├── environments.md                       # copier-answers.yaml, flags, drift, copier update
 │   ├── adding-a-resource.md                  # End-to-end walkthrough across all three layers
+│   ├── connecting-a-repo.md                  # Cluster-side: repo Secret, bootstrap, host key, SSO RBAC
+│   ├── connect-env-vars.md                   # Variables and flags for the connect operations
 │   └── cogarchhubgitops-reference.md         # The CogArchHubGitOps instance
 └── assets/
     └── example-cluster-resource/             # Starting templates for a new resource