Build UI mobile-first and accessible: mobile is the default canvas, every job works with a thumb and with a keyboard. Use when writing or changing JSX, CSS, layout, forms, navigation, or PWA screens, or when the user says a11y, accessibility, mobile-first, mobile, phone, touch, or /mobile-a11y. Do not use for browser-test craft (ui-verify) or TypeScript taste (code-quality-standards).
