Add Scrabble pattern with improved UI layout (commontoolsinc#2228)

feat: Improve scrabble pattern UI layout and interactions

- Center board, rack, header and instructions with consistent 540px max-width
- Move message display into rack bottom bar with styled text
- Move New Game button to header, style with green theme
- Style Clear Board button with brown theme matching rack
- Change default message to "Click New Game to begin"
- Add dropZoneRect to ct-drop-zone events for position calculations

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Co-authored-by: Tony Espinoza <tonyespinoza@Tonys-MacBook-Pro.local>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

Author: 3 people