next.js

9a76ce43 - Revert "Revert "Add a --webpack flag and default --turbopack to true (#84216)"" (#84351)

Revert "Revert "Add a --webpack flag and default --turbopack to true (#84216)"" (#84351) Reverts vercel/next.js#84348 which itself reverted #84216. In the 2nd attempt to make --turbopack a default behavior. * adjust the Generate Pull Request States action to specify `--webpack` * set the `IS_WEBPACK_TEST` flag in the deployment e2e tests (which are now [passing](https://github.com/vercel/next.js/actions/runs/18113062122)) * make the warning about having a webpack config without a turbopack config more verbose and consistently an error