enabled property
A local narrowing, ANDed with the package's own canReorder answer.
It can only ever narrow, never widen.
Prefer this to conditionally omitting the handle. Omitting it
changes the row's widget SHAPE, so Widget.canUpdate fails and the
framework re-inflates the whole row subtree, disposing whatever
State the app keeps beneath it.
Flipping this MID-DRAG does nothing to the live session, and needs
no backstop: the recognizer belongs to the row, not to this widget,
and the onPointerDown being nulled has already fired. Use
TreeReorderConfig.canReorder for a refusal that must interrupt a
drag in flight; the controller enforces that one for the session's
whole life.
Implementation
final bool enabled;