"Detach" cluster from Jupyter kernel

When I start a cluster from a Jupyter notebook and then shut down the notebook, the cluster will also shut down. Is there a way to detach a cluster from a notebook kernel?

Start by reproducing the lifecycle described in the issue: launch a cluster from a Jupyter notebook, then shut down the notebook kernel. Trace how the kernel owns or stops the cluster; done means a supported detach behavior lets the cluster continue running after kernel shutdown.

索引モデルが issue の本文から書いたものです。