The name being edited, or null when adding.
Error if the name is invalid or already taken — the panel surfaces it and keeps the
editor open.
Every edit is ONE undo entry. Each setter opens its own commit, so a rename plus a redefinition
would otherwise unwind a field at a time — and setName re-keys the item in the collection, so a
half-undone edit leaves the map keyed on something the item no longer carries.
Changing the SCOPE is not a field write at all but a delete plus a define, for the reason given at that branch; it is wrapped in its own commit to keep the same one-entry guarantee.
Applies a draft: defines a new name, or writes the changed fields of an existing one.