Agents home and a New agent page with an agent builder

In the UI: the Agents page shows each agent’s channels and triggers,
24-hour run bars and a Needs attention list for setup problems. Its
Channels view lists every channel in the organization with publish and
unpublish, people reached and fastest first reply. It replaces the Exposures
page; /exposures now redirects there.
New agent offers Describe, Example, Blank and Import. Describe drafts the agent with the utility model, and Create makes the agent with its draft channels and schedule trigger.
In code: everruns agents draft runs the same agent builder from the CLI.