curl --request GET \
  --url https://api.agentic.scope3.com/api/v2/buyer/advertisers/{advertiserId}/test-cohorts \
  --header 'Authorization: Bearer <token>'

{
  "cohorts": [
    {
      "id": "cohort_abc123",
      "advertiserId": "12345",
      "name": "West Coast Treatment Group",
      "cohortType": "geographic",
      "role": "TREATMENT",
      "definition": {
        "type": "zip_code"
      },
      "isActive": true,
      "createdAt": "2025-01-15T10:30:00Z",
      "updatedAt": "2025-01-20T14:45:00Z",
      "description": "<string>",
      "estimatedSize": 50000
    }
  ],
  "total": 6
}