ModifierNode

Base retained node for one active modifier description.

A creation hook returns a fresh instance, and the runtime owns it through detach and dispose after binding. Constructors initialize ordinary data; lifecycle callbacks acquire and release external resources. The default behavior is a one-child pass-through measure and layout. A modifier scope always exposes exactly one virtual child. An override may leave that child unmeasured or unplaced, which excludes the component subtree from later phases. Nodes are thread-confined by the owning tree. Subclasses implement only the typed capability interfaces whose behavior they provide.