[ingvarch]

What changes

Deleting the namespace the session is in moves the session to default only if it is still there when the cluster answers. Before, the move was decided when the key was pressed: if you went to :jobs staging before the answer came, the late answer took you from staging to default and said "The session is in default now."

• The delete always answers with the namespace it deleted. When the answer comes, the session moves only if it is in that namespace on the same connection; after a switch of clusters it stays, even when the new cluster has a namespace of that name.
• The status line says "Namespace X deleted." and adds "The session is in default now." only when the session moved. That text comes from one message, so it holds whichever of the two answers of the delete comes first; the done message of the delete only unmarks and reads the list again.
• A session that went into the namespace being deleted before the answer also goes to default, since every list there would be empty.
• docs/clients.md says this.

Closes #167

Checklist

• The test for this change was written first and failed
• make check is green
• The title is a conventional commit: feat(ui): ..., fix(nomad): ...