Fix: Serve preview scripts as virtual modules for Vite processing - #83

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/setup-node@v4, codecov/codecov-action@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Codecov: Failed to properly upload report: The process '/home/runner/work/_actions/codecov/codecov-action/v4/dist/codecov' failed with exit code 1