ST2110DeviceStateChanged

Device-wide lifecycle for an ST 2110 NMOS sender or receiver device. Independent of any individual sender/receiver: tracks how far through NMOS registration the device as a whole has progressed.

Sequence:

INITIALISING — gen_server up; NMOS register calls not yet issued REGISTERING — at least one resource (device / source / flow / sender / receiver) is awaiting first-registry confirmation READY — every currently-tracked resource is registered with at least one NMOS registry. An NMOS controller can discover the device and PATCH its senders/receivers. FAILED — bring-up rejected (validation, NMOS register call returned an error, etc.); reason carries detail.

READY is sticky for the current resource set but the device drops back to REGISTERING if a later contextChanged adds resources (so the "Ready" signal always accurately reflects "every resource we have right now is discoverable").