Mobile responsiveness: typography, touch targets, tablet & small-screen breakpoints

[s-adamantine]

Summary

Adds responsive CSS for mobile and tablet devices. Only globals.css is changed — no JS modifications.

What's new

• Mobile typography scaling (< 768px) — H1 32→26px, H2 24→20px, H3 16→15px
• Touch targets (< 768px) — sidebar links and hamburger button now meet 44px WCAG minimum
• Tablet breakpoint (769–1024px) — sidebar narrows to 220px, content padding reduced, H1 scaled to 28px
• Mobile header (< 768px) — header height 64→56px, logo scaled down, breadcrumbs scroll horizontally instead of wrapping
• Pagination (< 768px) — prev/next cards stack vertically
• Small mobile (< 480px) — sidebar uses 85vw width, tighter header and content padding

Breakpoints after this PR

Breakpoint	What it does
> 1400px	Wider sidebar (existing)
1025–1200px	TOC hidden (existing)
769–1024px	NEW — tablet layout
≤ 768px	Enhanced — mobile layout with touch targets, typography, header, pagination
≤ 480px	NEW — small mobile adjustments

Testing

Tested against: iPhone SE (375px), iPhone 14 (390px), iPad Mini (768px), standard desktop.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
hypercerts-atproto-documentation	Ready	Preview, Comment	Feb 16, 2026 10:43am
hypercerts-v0.2-documentation	Ready	Preview, Comment	Feb 16, 2026 10:43am

[s-adamantine]

Work already merged to main via direct commits. See commits ac33796, 67d28e0, b2ca35e for the CSS changes.