@peppered You are actually calling the global @quasar/cli, which in turn looks for @quasar/app in your node_modules, so it can pass project-oriented work to it. The global @quasar/cli is not finding the local @quasar/app, so you are getting that message. Another reason for getting that message, when you feel it is correct, if that node_modules has not been populated yet (like when you get your code from a repo, then forget to run yarn/npm on it).
@Akayy inside q-app is already vue, it’s the same as using it within other components. you can even test that in your codepen, move it out of the q-app div, or copy paste the inline-template multiple times. i dunno what you are trying to do at this point, so yep goodluck.