remark-lint-fenced-code-flag-case

remark-lint rule to warn when fenced code blocks have an inconsistently-cased language flag. Current stable version is 3.0.0, released as part of the unified-utils monorepo. Release cadence is irregular, with breaking changes tied to minimum node version bumps (now 20.18.0). Key differentiator: unlike similar lint rules, this enforces lowercase flags to ensure compatibility with tools like Prettier that may ignore uppercase or mixed-case flags. Full Unicode support is included. ESM-only, cannot be required with CommonJS.