52920747e1
The Docusaurus build step (198s) is 79% of the docs-site-checks job wall time and is the CI critical path. The site has two locales (en + zh-Hans, ~700 pages total); building only the default locale in PR checks halves the build time. Follows the same pattern Docusaurus uses internally: a build:fast script that runs `docusaurus build --locale en` for CI/preview builds, while the full bilingual build runs only in deploy-site.yml for production deploys. deploy-site.yml is unchanged — it still runs `npm run build` (all locales) on push-to-main and release.