Fix Vite 8 library React imports

[krowvin]

Summary

• configure the Vite 8 library build to convert external React require() calls into browser-compatible ESM imports
• use the current rolldownOptions configuration name
• declare @babel/parser, which the Lighthouse route extraction script imports directly
• verify the generated ESM bundle in the React 18/19 compatibility workflow

Background

@LaurenAllin reported in USACE-WaterManagement/groundwork-water#319 that updating Groundwork and Groundwork Water produced a browser error calling require("react"), and that returning to an earlier Groundwork version restored the application.

I reproduced that finding locally in a fresh Vite application with Groundwork Water 4.0.0 and Groundwork 4.3.1. The application built, but the browser rendered a blank page with the same require("react") error. The generated Groundwork ESM bundle contained Rolldown's runtime CommonJS fallback around React.

Vite 8 provides esmExternalRequirePlugin for this migration case. Applying it to Groundwork's React peer dependencies keeps React external while converting those calls to standard ESM imports.

Local verification

• npm test -- --run - 8 tests passed
• npm run lint
• React 18: library build, bundle verification, and docs build
• React 19: library build, bundle verification, and docs build
• npm pack --dry-run
• linked this Groundwork branch into a clean Groundwork Water checkout
• built the linked Groundwork Water library and documentation site
• served the linked production documentation build locally with React deduplicated for the symlinked peer dependencies; the page rendered with styles and no browser console errors

The bundle check fails if a future ESM build reintroduces the browser-side CommonJS fallback or a direct React require() call.

Related: USACE-WaterManagement/groundwork-water#319

[github-actions]

Please set a versioning label of either major-bump, minor-bump, or patch-bump to the pull request.