Added RC and final builds for iOS 26.7 and iPadOS 26.7.

Added third and fourth RC's, as well as final builds, for macOS Sequoia 15.8 and Tahoe 26.7.

Added seventh and eighth betas; RC and final builds for OS 27.0.

Dimmed wallpapers for iOS 27, iPadOS 27, and macOS 27 Golden Gate to improve readability.

Corrected typos in macOS High Sierra 10.13.6 Security Updates 2019-003 and 2019-004.