Dark Mode Regression Testing

The dark theme is now verified with DOM-level assertions instead of screenshot comparisons. The Playwright spec at tests/dark-mode.spec.js loads the homepage with the dark theme enabled and inspects computed styles for critical UI regions.

How the Test Works

Forces the theme preference to dark before any page scripts execute.
Confirms the <html> element applies data-theme="dark".
Checks computed background and text colors for body, the primary navigation bar, and the first rendered proof card.
Ensures interactive links in the navigation and proof card inherit the light text color expected in dark mode.

These assertions target CSS variables so regressions in the palette or class selectors are caught immediately without relying on binary diffs.

Running the Test Suite

Install dependencies (once per environment):
```
npm install
npm run test:browsers
```
Execute the dark-mode check:
```
npm test
```
or run only this spec:
```
npm run test:dark
```

Playwright starts the Eleventy dev server automatically. No manual screenshot curation is required, and the repository contains no .png baselines or snapshot folders.