Function dispatch_synthetic_goodbye 

async fn dispatch_synthetic_goodbye(
    ctx: &Arc<ServerCtx>,
    conn_id: u64,
    registered_pid: Option<u32>,
)

Phase E.1b — synthetic Goodbye dispatch for ungraceful disconnects (EOF / read error before the client sent an explicit Goodbye). Without this, the reducer’s process record stays Running and a reconnect from the same live PID hits AlreadyRegistered. (codex P1 #610.)