[Bug]: container k8s list shows an empty cluster name for the default control-plane node

[Hokila]

Steps to reproduce

1. On apple/container main at d265d669ecae041bf338cb3b39c4118316d138f0, create a cluster with the default container k8s create path.
2. Run container k8s list and inspect the CLUSTER column for the k8s-dev control-plane node.

I reproduced the underlying list-row behavior in a focused regression test against this clean main revision, using a ContainerSnapshot with ID k8s-dev and role label control-plane,worker (the label written by the default create path). K8sHelper.buildK8sRows(from:) produced a row whose clusterName was ""; the expected value was "k8s-dev". This focused test did not require a running container service. I have not separately run the end-to-end CLI steps above.

Problem description

The default k8s create path gives the control-plane node both control-plane and worker roles. LinuxNodeProvisioner joins them into the single role label control-plane,worker.

buildK8sRows recognizes a control-plane node only when the whole label equals control-plane. It therefore treats the default node as a worker. Because k8s-dev does not contain -worker-, the orphan-worker name derivation returns an empty cluster name. k8s list renders these rows directly.

Expected: the default node is listed under cluster k8s-dev, and matching worker nodes are grouped under it.

Actual in the focused regression test: the control-plane row has an empty cluster name. The CLI display and grouping impact follows from the same row-building path.

Environment

• OS: macOS 26.6.2, Apple Silicon
• Xcode: 27.0
• Swift: 6.4 development snapshot
• Container source: apple/container main at d265d669ecae041bf338cb3b39c4118316d138f0