remove browse mode and code that became dead as a result of its removal, because the new plan is to launch the program from the terminal (and terminal navigation is okay)

fcore/app-update.sml

@@ -5,6 +5,5 @@ struct
   fun update (model: app_type, inputMsg) =
     case #mode model of
       NORMAL_MODE => NormalMode.update (model, inputMsg)
-    | BROWSE_MODE => BrowseMode.update (model, inputMsg)
     | MOVE_MODE => MoveMode.update (model, inputMsg)
 end