The contract between the model and platform backends.
net-lattice-platform depends only on net-lattice-core — never on
net-lattice-model. Its provider traits describe the shape of a
contract, not the content of the model, via associated types. See
ARCHITECTURE.md for the full rationale, including how model
convergence is enforced one layer up, in lattice.
Stage 0.1 includes only RouteProvider — InterfaceProvider,
NeighborProvider, DnsProvider, and EventProvider are added in
later stages per ARCHITECTURE.md's Incremental Delivery Plan.