meta {
  name: List Instances
  type: http
  seq: 1
}

http {
  method: GET
  url: {{coordinatorBaseUrl}}/api/coordinator/instances
  auth: none
}

headers {
  Accept: application/json
}

notes {
  Returns all known core instances from the in-memory registry.
  Registry is populated via gRPC heartbeats from core instances.

  Response: InstanceMetadata[]
    instanceId:        string   — unique instance ID
    hostname:          string
    httpPort:          int
    grpcPort:          int
    subscriptionCount: int      — number of active game subscriptions
    localCacheSize:    int
    lastHeartbeat:     string   — ISO-8601 timestamp
    state:             string   — "HEALTHY" | "DEAD"
}