Watch the sandbox's screen

multipart/x-mixed-replace; boundary=pistis-frame, for as long as you read it. Each part is a picture (image/jpeg, with X-Screen-Width and X-Screen-Height when known), sent only when the screen changed, or application/json {"none": "<why>"} while there is no picture (no browser open yet, the agent isn't using the sandbox). The sandbox makes pictures only while someone watches; a slow reader gets the newest picture, never a backlog. Nothing is recorded. Whoever may read the session may watch it.