Required design CI currently adds roughly 3½ minutes to each PR and blocks intentional redesigns or harmless changes in axe-generated selectors. Replace that step with 14 browser behaviour checks using CI's installed Chromium; retain required token and design-record enforcement.

Screenshot comparisons and exact contrast-report checks remain available on demand through `bun run design:browser`. Keyboard navigation, focus, form errors, reduced motion, reflow, scrolling, and production audit exclusion remain required.

Validation: `bun run ci`, `bun run types`, 55 design-check unit tests, and all 14 behaviour checks passed. The behaviour suite took 29.6 seconds locally on macOS and passed in 40 seconds on GitHub Linux CI, versus the previous 3m32s visual step on main (about 2m52s saved). The remaining system E2E and container jobs are still running. The optional suite still discovers all 38 tests. No screenshot or contrast baselines changed.

### CI flow