Why: EXT-11 is accepted; the surface (SetScopedHostFactory/NewScopedHost, SurfaceVersion 2.4.0-experimental) must land with the behavioral red pinned - wiring absent, NewScopedHost fails closed with ErrNotLinked.
Evidence: TestScopedHostFactory red at the wired-factory assertion; row follows on the task card.
Impact: pkg/extension additive surface (surface.txt +2 symbols); internal wireScopedHostFactory stub. Behavior unchanged.
Refs: EXT-11 proposal; task card.