client: Improve documentation of ClientApp and ClientAppInstance

js/src/main/scala/cs214/webapp/client/ClientApp.scala

@@ -3,14 +3,12 @@ package client
 
 import org.scalajs.dom
 
-/** The ClientApp interface is used by clients to connect to a server. */
+/** A factory for client-side app instances. */
 trait ClientApp:
   def appId: AppId
-  def uiId: UIId 
+  def uiId: UIId
   def init(instanceId: InstanceId, userId: UserId, endpoint: String, target: dom.Element): ClientAppInstance
 
-/** The ClientAppInstance interface is used by the server to store the state of
-  * a client UI.
-  */
+/** An instance of a client-side application. */
 trait ClientAppInstance:
   def onMessage(msg: util.Try[ujson.Value]): Unit