curl https://api.getspine.ai/v1/canvas/<canvas_id>/tasks/<task_id> \
  -H "X-API-KEY: sk_spine_..."

{
  "success": true,
  "data": {
    "task_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
    "name": "<string>",
    "status": "completed",
    "children": "<array>"
  }
}

{
  "success": false,
  "error": "X-API-KEY header required"
}

{
  "success": false,
  "error": "Run not found: 550e8400-e29b-41d4-a716-446655440000"
}