Four ways erase a derived port and take no edge with them: deleting a state,
deleting the `State machine` literal, deleting `Behavior start`/`end`, deleting
the asset. The common cause is `RemoveNodeCommand` clearing only its own graph,
so the fix sits in `drawnDef` (graph/nested.ts) and touches no delete site.
A right-click on an edge goes through `view.portAt` only — there is no curve
hit-test. Without a port row such an edge is not merely invisible, it is
unreachable, so the ghost row is the handle Disconnect hangs on.
`resolveDef` stays untouched: it is the truth for interpreter, compiler,
ConnectCommand and dropTarget, so nothing runs or connects through a ghost
without a second guard.
