Which feature-builds transport redundancy by using the cross link between two redundant WAN Edge routers?

OMP is the SD-WAN overlay routing protocol responsible for distributing routes and TLOC reachability; it does not provide the cross-link transport redundancy mechanism between co-located routers.

Zero-touch provisioning automates the onboarding of new devices to the SD-WAN fabric and is entirely unrelated to transport redundancy between co-located branch routers.

Quality of service prioritizes traffic types within existing tunnels and does not create or extend transport redundancy between routers sharing a WAN connection.

TLOC extension allows a WAN Edge router that lacks a direct transport connection to borrow the TLOC of an adjacent WAN Edge router through a cross-connect link, typically implemented as a GRE tunnel. This provides transport redundancy at a branch without requiring each router to have its own dedicated physical WAN circuit.