Add visual regression testing #3430

Congrats on the release! Astryx looks really nice, and it's cool what you're building here.

Astryx ships 150+ components across 7 themes with light/dark mode, which is a lot of visual surface area to keep consistent as the system evolves, especially if you are considering RTL as well. I noticed @axe-core/playwright is already wired in for a11y checks, but there's no visual regression tooling on stories yet, so purely visual regressions (spacing, color, a broken theme override) could land undetected as commits accumulate.

Proposal

I'm one of the co-founders of Happo, along with @trotzig (disclosure, since I think that's relevant context here). It's a visual regression and accessibility testing service that plugs into Storybook (among other tools). Flagging it because it seems like a solid fit for Astryx specifically:

• Storybook-native: point it at apps/storybook and it screenshots every story automatically, no per-story config needed to get started.
• Cross-browser and theme coverage: given Astryx's 7 themes x light/dark, Happo can snapshot every combination and diff them independently, so a regression in one theme doesn't get masked by the others.
• Built-in accessibility testing: Happo also runs axe-core checks alongside the visual diffs, so a11y results and visual diffs show up in the same PR check instead of two disconnected tools. This is optional, so you can continue to use your current accessibility testing setup if you prefer.
• GitHub PR integration: diffs show up as a status check with inline before/after comparisons, reviewers approve or reject directly.
• Free for qualifying open source projects, generous quota, no cost to the project.

Why raise this now

Astryx is early and moving fast, so this is the cheapest point to add a visual safety net, before the story count and theme surface get even bigger.

Happy to help set this up if there's interest. @trotzig and I are also happy to answer questions!