• Added locale fallback support for Gutenberg/script translation JSON files.
• Extended filename fallback logic to handle domain-locale-hash.json patterns in addition to .mo and .l10n.php.
• Added support for variant locale fallback such as de_DE_formal -> de_DE.
• Improved fallback chain order to prefer same-language locales before global English fallback.
• Added final English fallback support (en_GB / en_US) when no matching locale is available.
• Introduced lightweight in-request caching for fallback chains and resolved files.
• Kept compatibility with classic WordPress translation loading and modern translation file loading.
