struct DetachCmd

Detaches a parentable object from its parent (e.g. a node from a parent node,

or a layer from a layer stack). It is illegal to apply this command to a

non-parentable object. No-op if the target object currently has no parent.

Constraints:

- `id` refs a parentable object

Discussion:

For nodes, this command will detach a node from its parent, regardless of

whether it is a part or a child of its parent.