Rollup: Change the output destination of an input html file

Question

While building I wish to change the output destination to an input file when using rollup+vite.

An Example MVE:

Input

src/
| foo/
| | foo.html
| bar
| | bar.css

Desired Output

dist/
| foo.html
| assets/
| | name.css

Current Output

dist/
| src/
| | foo/
| | | foo.html
| assets/
| | name.css

vite.config.js

export default defineConfig({
  plugins: [svelte(), splitVendorChunkPlugin()],
  build: {
    rollupOptions: {
      input: {
        app_timesheet: "./src/foo/foo.html"
      },
      output: {
        /* .. ?? .. */
      }

    },
  }
})

So far I have tried augmenting the output.assetFileNames but when returning the name, the function does not change the path.

I have also tried using the Roll-Up Plugin API, but I can't seem to find a build or output hook that is relevant.

Any Help or Advice would be apricated.