curl --request PATCH \
  --url https://brew.new/api/v1/automation/runs \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "automationRunId": "run_01HZ",
  "status": "cancelled",
  "reason": "recipient unsubscribed"
}
'

{
  "error": {
    "code": "NOT_IMPLEMENTED",
    "type": "not_implemented",
    "message": "This endpoint shell is ready, but the business logic is not implemented yet.",
    "suggestion": "Cancel is part of the P7 work; tracked in docs/email-automations-architecture.md §7.4.",
    "docs": "https://docs.brew.new/api-reference/api/errors"
  }
}