[BUG] Action fails when devEngines packageManager is set to pnpm

### Action config

```yaml
- uses: FirebaseExtended/action-hosting-deploy@v0
with:
repoToken: "${{ secrets.GITHUB_TOKEN }}"
firebaseServiceAccount: "${{ secrets.FIREBASE_SERVICE_ACCOUNT_OTHELLO_RUST }}"
channelId: live
projectId: othello-rust

```

#### package.json
```json
"devEngines": {
"packageManager": {
"name": "pnpm",
"version": ">=11"
},
"runtime": {
"name": "node",
"version": ">=26"
}
}
```

### Error message

```
npm error code EBADDEVENGINES
npm error EBADDEVENGINES The developer of this package has specified the following through devEngines
npm error EBADDEVENGINES Invalid devEngines.packageManager
npm error EBADDEVENGINES Invalid name "pnpm" does not match "npm" for "packageManager"
npm error EBADDEVENGINES ***
npm error EBADDEVENGINES current: *** name: 'npm', version: '11.13.0' ***,
npm error EBADDEVENGINES required: *** name: 'pnpm', version: '>=11' ***
npm error EBADDEVENGINES ***
...
Error: The process '/opt/hostedtoolcache/node/26.2.0/x64/bin/npx' failed with exit code 1
***
conclusion: 'failure',
output: ***
title: 'Deploy preview failed',
summary: "Error: The process '/opt/hostedtoolcache/node/26.2.0/x64/bin/npx' failed with exit code 1"
***
***
```

Full logs: https://github.com/nstringham/othello-web-app/actions/runs/26340171515/job/77540738605

### Expected behavior

The action works correctly with npm, yarn, or pnpm

### Actual behavior

The action fails when using pnpm