Bug Fix:
- Backend was defaulting to mobile (isMobile ?? true)
- Frontend was defaulting to desktop
- Changed runner.js default to false (desktop) to match frontend
Feature Integration:
- Added Waterfall button to each history item
- Added comparison checkboxes to history for easy test selection
- Auto-limit to 2 tests for comparison
- Comparison controls appear dynamically when tests selected
- Auto-load comparison when URL params present