refactor(agent): move the device list and re-apply plan into orchestrator/devices.rs

orchestrator.rs held the Orchestrator and, below its impl, 270 lines of free functions about the device list rather than the orchestrator: building AgentDevices from an inventory snapshot in carousel order, deriving the host-switch links and the configured wheel mode, matching devices across ticks by stable identity, and planning which ones re-apply their volatile settings and how many confirming passes they get. That is devices.rs now; the orchestrator keeps the RwLock and watch-publication helpers, which are about its own shared state, and reaches the rest through one use. Its tests import the same names from super as before.

Pure move: no line inside the moved items changed beyond pub(super) on what the orchestrator and its tests call.