dsh-kube-lens: Add a default read-only Kubernetes cluster browser to DSH

The DSH plugin maintained by atticuswx accesses clusters via kubectl using kubeconfig. The sidebar provides a resource explorer, while panels support namespace filtering, anomaly filtering, YAML editing (CodeMirror 6), and SSE-followed logs. It also exposes six read-only Agent tools: kube_contexts, kube_get, kube_describe, kube_logs, kube_events, and kube_diagnose, where the latter outputs troubleshooting conclusions backed by evidence. By default, it is read-only, and Secret content is never returned; write operations require sequential approval once allowWrites is enabled. It requires kubectl on the host machine and is licensed under the MIT License.