* feat(web): make web UI mobile responsive
Fixes#2274
Add mobile-first responsive design to the GSD web UI:
- Viewport meta tag via Next.js Viewport export
- Collapsible sidebar as slide-out drawer on mobile with hamburger menu
- Milestone explorer as right-side drawer on mobile with bottom bar toggle
- Responsive header: hide project label, scope badge, beta badge on small screens
- Dashboard: responsive grid (1col mobile -> 2col sm -> 4col xl), responsive padding
- Status bar: hide secondary info on small screens, responsive text sizing
- Touch-friendly 44px minimum tap targets on mobile nav items
- Mobile CSS utilities in globals.css (overlay, drawer transitions)
- 19 structural tests verifying responsive classes exist in key components
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
* ci: retrigger after stale check
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Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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