Also let the user switch Skip branches to Deep (widening; needs Clone Records: Override Scope).
Fires when the user switches a branch's policy; the host re-plans with it as an edge override.
Fires when the user selects a node row.
Key of the node to highlight, e.g. when the review step links back to it.
Blocked only because prompted values haven't been entered yet: not a problem on the Scope step.
The plan to render. Setting it rebuilds the tree.
The policy a click on this edge's pill would switch to, or null when the pill is read-only.
Let the user switch unlocked Deep branches to Skip (narrowing). Default false (read-only tree).