Returns live calls straight from the switch (FreeSWITCH channels), NOT the dialer_calls database table that /calls reads. Use this to see calls that never write a dialer_calls row — notably API click-to-call / originate calls made without a campaign_id — plus pre-answer/ringing and unbridged legs. One entry per live leg; bridge_uuid links the two legs of a bridged call. Requires calls:read.