Implement a mobile-friendly settings interface for the worksheet generator:
**Mobile Layout (< 768px):**
- Full-screen worksheet preview
- Floating draggable settings button showing current config summary
- Settings drawer slides in from left (90% width, max 400px)
- Swipe-left gesture, backdrop click, or Escape key to close
**Desktop Layout (>= 768px):**
- Keeps existing resizable panel layout with grab tab
- No changes to desktop UX
**Draggable Settings Button:**
- Drag anywhere on screen with safe 16px margins
- Never overlaps nav bar or action buttons (constrained to safe zone)
- Position persists in localStorage
- Visual feedback: grab/grabbing cursor, elevated shadow while dragging
- Smart click detection: only opens drawer on click, not after drag
**Settings Summary:**
- Shows human-readable config with icons (➕📄🎨🎯)
- Multi-line format: operator, layout, scaffolding, difficulty
- Updates live as settings change
**New Components:**
- useMediaQuery hook for responsive breakpoint detection
- MobileDrawer with backdrop and animations
- MobileSettingsButton with drag-and-drop
- ResponsivePanelLayout wrapper (conditionally renders mobile or desktop)
- generateSettingsSummary utility with icon system
**Integration:**
- AdditionWorksheetClient now uses ResponsivePanelLayout
- Single codebase handles both mobile and desktop seamlessly
- No breaking changes to existing desktop functionality
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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