native packaging is indeed a hot topic. the chromium team wants to do it: https://v8.dev/features/modules#web-packaging
no clue about when it will be ready & other browsers.
we can use a manifest (& service worker) for app related images & css.
regarding the .mjs files it is tricky though: the main thread is using very(!) few files in neo.mjs, while the app worker consumes a lot (most parts of the framework & app files).
as far as i know there is nothing like a manifest for the worker scope out there (did not search for it for a long time). please give me a heads up in case there is!