How can I have the app find approximateTerrainHeights.json, etc.?

I have a sample app at my-vue-app which demonstrates the problem.

The app builds and starts to run, but I get a lot of errors like:

Resource.js:2256     GET http://localhost:5173/Assets/approximateTerrainHeights.json 404 (Not Found)
bingAerial.png:1     GET http://localhost:5173/Widgets/Images/ImageryProviders/bingAerial.png 404 (Not Found)
TouchRotate.svg:1    GET http://localhost:5173/Widgets/Images/NavigationHelp/TouchRotate.svg 404 (Not Found)
Resource.js:2256     GET http://localhost:5173/Assets/Textures/SkyBox/tycho2t3_80_mx.jpg 404 (Not Found)

Based on the “Configuring CESIUM_BASE_URL” section at CesiumJS Quickstart

In main.js, I have set:

window.CESIUM_BASE_URL = '';

I have tried changing vite.config.js to:

import { defineConfig } from 'vite'
import { join } from 'path';
import serveStatic from 'serve-static';
import path from 'path';

import vue from '@vitejs/plugin-vue'

export default defineConfig({
  plugins: [

  server: {
    middleware: [
      serveStatic(join(__dirname, 'node_modules', 'cesium', 'Build', 'Cesium'))

to try to serve the directories as static files. The behavior did not change.

I am not sure what more I need to do to make this work.

Does anyone have any advice?

Note, this app will eventually be run offline. I will not be using Cesium Ion.