Proposition: Schedule support bound

An output observable pulls back to an observable supported in its scheduled backward support. Thus interventions outside that support cannot change its unconditional outcome law. If every block has supplied diameter at most $r$, a depth-$L$ backward support lies within supplied distance $Lr$.

Proof. Blocks disjoint from the next support act on identity factors and their adjoints preserve those identities. Induct backward through the layers. The distance statement follows by adding at most one block diameter per layer.