CJS module package code that contains "typeof window === 'undefined'" checks are not excluded from app router client builds

### Link to the code that reproduces this issue https://github.com/adanperez/nextjs-cjs-package-bug ### To Reproduce 1. Start the application after installing. `yarn dev` 2. Navigate to http://localhost:3000/cjs ### Current vs. Expected behavior Next.js seems to be including server code when compiling the client code for the browser. For a CJS module package used on an app router page, the Next.js build is ignoring the `typeof window === 'undefined'` check when compiling the client code. In this case it is trying to add `node:` prefixed packages that `undici` is using. The `undici` code should only be referenced in the server code and not in the client code. You will see the following node prefix import error if you go to http://localhost:3000/cjs where that package is being used. ``` Build Error Failed to compile node:assert Module build failed: UnhandledSchemeError: Reading from "node:assert" is not handled by plugins (Unhandled scheme). Webpack supports "data:" and "file:" URIs by default. You may need an additional plugin to handle "node:" URIs. ``` If you have that samne CJS module package code local to the project in the `src` directory, it will work as expected. It will not include the `undici` code path. See http://localhost:3000/local. (you may have to restart the app if you triggered the bug from the other link) ### Provide environment information ```bash Operating System: Platform: darwin Arch: arm64 Version: Darwin Kernel Version 23.4.0: Fri Mar 15 00:10:42 PDT 2024; root:xnu-10063.101.17~1/RELEASE_ARM64_T6000 Available memory (MB): 32768 Available CPU cores: 10 Binaries: Node: 20.12.2 npm: 10.5.0 Yarn: 1.22.19 pnpm: 8.15.1 Relevant Packages: next: 14.3.0-canary.65 eslint-config-next: 14.2.3 react: 18.3.1 react-dom: 18.3.1 typescript: 5.4.5 Next.js Config: output: N/A ``` ### Which area(s) are affected? (Select all that apply) SWC, Webpack ### Which stage(s) are affected? (Select all that apply) next dev (local), next bu…