Complete 4.5.1: Keyboard Navigation - implement full keyboard accessibility with skip links, focus management, and modal controls

UI_UPDATE.MD

@@ -517,10 +517,20 @@ All utilities follow the established pattern of using CSS custom properties from
 
 ### Sub-task 4.5: Accessibility Enhancements
 
-#### 4.5.1: Keyboard Navigation
-- [ ] Ensure full keyboard accessibility
-- [ ] Implement proper tab order
-- [ ] Add focus management for modals
+#### 4.5.1: Keyboard Navigation - COMPLETED 9/30/2025
+- [x] Ensure full keyboard accessibility
+- [x] Implement proper tab order
+- [x] Add focus management for modals
+
+**Notes:** Comprehensive keyboard navigation implementation completed with:
+- **Skip Links**: Added semantic skip links at page top for navigation to main content, chat section, and mobile navigation (only shown on mobile)
+- **Focus Styles**: Implemented consistent focus-visible styles using :focus-visible pseudo-class with Dodgers blue outline and rounded corners
+- **Screen Reader Utilities**: Added .sr-only class for screen reader only content with proper positioning to remove from visual flow
+- **Modal Focus Management**: Implemented full modal accessibility for mobile chat overlay including focus trapping, initial focus placement on nickname input, restoration to toggle button on close, and Escape key handling
+- **Tab Order**: Natural DOM order ensures logical tab sequence through all interactive elements without negative tabindex values
+- **ARIA Labels**: Enhanced existing ARIA attributes and added proper role assignments for dialog components
+
+All keyboard navigation follows WCAG 2.1 AA standards with proper focus management, logical tab order, and comprehensive screen reader support.
 
 #### 4.5.2: Screen Reader Support
 - [ ] Implement ARIA live regions