Update Node.js to >= 24.0 and Yarn to 4.18.1 for Horizon Aid theme

Problem/Motivation

Node.js 20 reached end of life on 30 April 2026, and Drupal core main now requires "node": ">= 24.0" in core/package.json. The Horizon Aid theme still pins Node 20 in its engines and GitLab CI.

Node 24 is the LTS line, latest v24.22.2, and it is one of the lines the November 2026 security releases will patch. Pinning the major picks those patches up with no further change. Local systems should use Node.js 24 or 26.

Steps to reproduce

1. On 1.0.x, open package.json: the engines say "node": ">= 20.0" and "yarn": ">= 4.9.3", and packageManager is yarn@4.9.3.
2. Open .gitlab-ci.yml and .gitlab-ci-local.yml: the jobs run node:20.

Proposed resolution

• package.json engines: "node": ">= 24.0". Yarn moves to yarn@4.18.1 with the floor ">= 4.18.1", and .yarnrc.yml follows the Varbase standard (approvedGitRepositories, enableScripts, nodeLinker: node-modules, npmMinimalAgeGate: 0), which Yarn before 4.14.0 rejects.
• .gitlab-ci.yml and .gitlab-ci-local.yml: node:24 for the build and lint jobs.
• .gitlab-ci.yml: the composer and stylelint jobs set YARN_RC_FILENAME: .yarnrc.core.yml and YARN_NODE_LINKER: node-modules, so Drupal core's own Yarn 4.9.1 in those jobs does not read the project .yarnrc.yml, whose keys need Yarn 4.14.
• scripts/install-needed-tools.sh: NodeSource setup_24.x instead of setup_18.x.
• AGENTS.md: Node.js 24 or 26 and Yarn 4.18.1.
• yarn.lock is removed and .gitignore now ignores yarn.lock, package-lock.json and pnpm-lock.yaml, so installs resolve from package.json. CI already sets YARN_ENABLE_IMMUTABLE_INSTALLS to "false". The compiled CSS is not rebuilt in this change: CI builds the theme but does not compare the output with the committed files.
• Dependency ranges in package.json use carets, the way Drupal core writes them: exact versions, ~ and .x ranges become ^MAJOR.MINOR.PATCH, with no major bump.

AI-Generated: Yes

Remaining tasks

• ✅ File an issue
• ✅ Addition/Change/Update/Fix
• ✅ Testing to ensure no regression
• ➖ Automated unit testing coverage
• ➖ Automated functional testing coverage
• ➖ UX/UI designer responsibilities
• ➖ Readability
• ➖ Accessibility
• ➖ Performance
• ➖ Security
• ➖ Developer Documentation
• ➖ User Guide Documentation
• ❌ Reviewed by human
• ❌ Code review by maintainers
• ❌ Full testing and approval
• ❌ Credit contributors
• ❌ Review with the product owner
• ✅ Release notes snippet
• ✅ Release

User interface changes

• N/A

API changes

• N/A

Data model changes

• N/A

Release notes snippet

• Node.js 24 or newer is now required, in the engines and CI. Yarn 4.18.1 is the package manager.