ST2110ReceiverStateChanged

Lifecycle state of a single receiver inside an ST 2110 NMOS input device. The receiver_label keys events to the configured receiver; state follows the sequence below. The endpoints / wire-format payload is populated only on ACTIVE so a client UI can render the negotiated transport without having to fish it out of separate IS-04/IS-05 traffic.

Sequence (per receiver):

IDLE ↓ (controller PATCH master_enable=true) STARTING { receiver_label } ↓ (first valid context arrives from the MTL RX session) ACTIVE { receiver_label, endpoints[], wire_pixel_format } ↓ (controller PATCH master_enable=false, or another switch) IDLE

At any point: FAILED { receiver_label, reason } — config rejected (e.g. unsupported wire transport), or the child workflow died without our asking (MTL session crashed, NIC dropped, etc.).

Mirrors the pattern of ST2110SenderStateChanged.