Move the four iPhone viewport descriptors (SE, 15/16, 16/17 Pro, Pro Max)
into tests/e2e/fixtures/devices.ts so the upcoming visual spec (Task 23)
can share the same anchors. The mobile-audit spec now spreads each
descriptor and adds a slug `name` plus a human `label` for the run header.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
