Class ResidencyApi

Boot seam (idempotent): install the residency sweeps. Today that's the real-time cold-tail eviction sweep; the deferred reset sweep will be installed here too. Activation = the ResidencyLogic singleton's presence. Eviction ships in observe mode (residency.eviction.mode), so booting culls nothing until an operator flips it to enforce.

Run one eviction sweep now (test / manual seam).