Pair holds both models and decides which answers. A prober asks the
remote whether it will take work and caches the answer, so a request
reads an atomic bool rather than paying for a health check. Routing sits
at p50 825ms on the hot path and must never wait on a machine that may be
asleep.
The two methods are the two halves of the degradation rule in
docs/offload.md. Complete falls back silently, for routing, replies and
nudge phrasing, where the big model is only better. CompleteRemote
returns ErrRemoteUnavailable instead, for a world question, where the
1.7B does not answer worse but invents.
A nil remote is the unconfigured deploy: nothing probes, everything goes
to the floor, and the box behaves exactly as it does today.
