List channels that are currently broadcasting. This is not the same as online on a channel object, which only means the channel is enabled for playback.

GET /v2/online-channels. A successful call returns 200 with an online_channels array. Each item has:

• live_channel_id - channel uuid
• online_since - Unix timestamp in seconds, returned as a string
• online_since_date - the same instant as ISO-8601

This list does not include title or encoder config. Look those up with Lookup Stream using live_channel_id.