Live events

Create canvas snapshot
-> append patch events
-> persist event log
-> stream updates to viewers and API subscribers

{
  "canvas_id": "canv_123",
  "event_id": "evt_456",
  "actor": "agent:openclaw",
  "type": "canvas.patch",
  "patch": [
    {
      "op": "replace",
      "path": "/blocks/0/props/markdown",
      "value": "Audit completed. Found 317 misfires."
    },
    {
      "op": "replace",
      "path": "/data/summary_metrics/misfires",
      "value": 317
    }
  ]
}