Add comprehensive draggable playing guide modal with quick navigation:
- Draggable modal on desktop, fixed on mobile
- 5 quick-access sections: Overview, Pieces, Capture, Harmony, Victory
- Integrated PieceRenderer SVGs for visual piece examples
- Responsive layout for desktop and mobile
- Modal persists during gameplay
- "How to Play" button on setup page with updated description
- "Guide" button in gameplay controls
- Complete guide content from PLAYING_GUIDE.md
Features:
- Desktop: draggable modal that can be positioned anywhere
- Mobile: full-screen responsive modal
- Quick navigation tabs for easy reference
- Visual piece examples with movement descriptions
- Mathematical capture relations explained
- Harmony progression examples with formulas
- Strategy tips and victory conditions
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>
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