curl --request GET \
  --url https://agenticadvertising.org/api/registry/publishers

{
  "publishers": [
    {
      "domain": "<string>",
      "member": {
        "slug": "<string>",
        "display_name": "<string>",
        "membership_tier": "<string>",
        "membership_tier_label": "<string>",
        "is_founding_member": true
      },
      "agent_count": 123,
      "last_validated": "<string>",
      "has_valid_adagents": true
    }
  ],
  "count": 123
}