Build with inverted colors to support dark mode

Nobody has claimed this yet.

This might be a nice way of supporting dark mode in Studio: either by automatically supporting an inversion for some color:

```css
.bg-white { background: #FFF; }

@media (prefers-color-scheme: dark) {
.bg-white { background: #000; }
}
```

Or creating additional classes to target what the inversion should be:

```css
@media (prefers-color-scheme: dark) {
.bg-white--dark-mode { background: #FFF; }
}
```

The issue names no files, tests, or entry points. Start by locating Assembly’s color classes and existing build or CSS-generation workflow, then compare the proposed prefers-color-scheme approaches with the project’s conventions. Done means a decided dark-mode strategy is implemented consistently and its behavior is verified.

Written by the indexing model from the issue text.