Release v2.3.1: Complete type checking fixes and responsive UI improvements - Fixed all type checking errors in test_bigwig_validation.py - Enhanced type narrowing with proper assert statements for mypy compatibility - Fixed HTTPError instantiation with proper EmailMessage headers - Removed duplicate test files for code consistency - Fixed responsive project info widget overlapping navigation on narrow screens - Enhanced z-index handling (1000-1001) for proper widget layering - Added mobile-friendly modal behavior with close buttons and backdrop - Implemented smart responsive breakpoints for all screen sizes - Updated all version references to v2.3.1 consistently across: - jbrowse_batch_tracks.py (__version__) - README.md (version badge) - docs/index.md (version info) - mkdocs.yml (project info) - Updated CHANGELOG.md and docs/changelog.md with comprehensive v2.3.1 entries - Maintained consistent documentation and version info across all files - Standardized type checking patterns across entire test suite - Improved test file organization and naming consistency - Enhanced code quality and maintainability