fn udp_key(address: &str, port: u16) -> StringExpand description
A UDP peer’s key: the address its reply came from and the port it serves.
Not the instance id. That is v<version> (the launcher’s AGENTMUX_INSTANCE_ID),
so every machine on the same release shares it, and keying on it merged two
such machines into one entry that flapped between them (Codex P1 on #4241).