FR: Nodes collapsed to small size or when no labels are requested, add label as a tooltip

### Description

When a flow has Nodes collapsed to small size (hide label option) or when the flow renderer has `labels:false` option, it would be good to show the label as a tooltip. Node-RED does this.

No files, tests, or entry points are named. Start by locating the renderer's node-label and collapsed-node handling, then inspect how the `labels:false` option is applied. Done means a node label is available as a tooltip both when labels are hidden by size and when labels are disabled.

Written by the indexing model from the issue text.