Enable some extra lints for compass app client (#2560)

Enable a few more lints that were mostly followed already for
consistency.

compass_app/app/test/utils/command_test.dart

@@ -48,7 +48,7 @@ void main() {
     });
 
     test('should only run once', () async {
-      int count = 0;
+      var count = 0;
       final command = Command0<int>(() => Future.value(Result.ok(count++)));
       final future = command.execute();