Build Artifact Not Found TurboRepo Nextjs

### Before opening, please confirm:

- [x] I have checked to see if my question is addressed in the [FAQ](https://github.com/aws-amplify/amplify-hosting/blob/master/FAQ.md).
- [x] I have [searched for duplicate or closed issues](https://github.com/aws-amplify/amplify-hosting/issues?q=is%3Aissue+).
- [x] I have removed any sensitive information from my code snippets and submission.

### Amplify Hosting feature

Deployments

### Is your feature request related to a problem? Please describe:

**Environment**

- Framework: Next.js 16 (App Router) with output: 'standalone'
- Monorepo: Turborepo
- Package Manager: pnpm 10.19.0
- Node.js: >= 20.10.0
- React: 19
- App Location: apps/web

**amplify.yml Configuration**

```
version: 1
applications:
- appRoot: apps/web
frontend:
phases:
preBuild:
commands:
- corepack enable
- corepack prepare pnpm@latest --activate
- pnpm install
build:
commands:
- cd ../..
- pnpm turbo run build --filter=web
artifacts:
baseDirectory: .next
files:
- "**/*"
```

Build completes successfully, but deployment fails with an error indicating the build artifacts cannot be found.

I can download the build artifacts in the console, and it all appears to be there, but the deploy step cant seem to find them.

```
[INFO]: Build Artifacts not found.
[ERROR]: {"code":"MissingBuildArtifacts"}
```

### Describe how you'd like this feature to work

After a successful build, Amplify should find the .next directory at apps/web/.next and deploy the application.

Start by reviewing the shown amplify.yml configuration, especially appRoot apps/web, the build command's change to the repository root, and artifacts baseDirectory .next. Verify where Amplify resolves the artifact directory after the build; done means the deployment finds apps/web/.next and successfully deploys the Next.js application.

Written by the indexing model from the issue text.