fix: enable GCP credential file and environment variables for Claude access (#91)

* fix: update all GitHub Actions to latest versions for Node.js 24 full support

- Update actions/checkout from v4.2.2 to v7.0.1
- Update google-github-actions/auth from v2.1.4 to v3.0.0

These versions are fully compatible with Node.js 24 and eliminate all
deprecation warnings in workflow logs.

* fix: enable GCP credential file and environment variables for Claude access

Claude needs access to GCP credentials to authenticate with Vertex API.
Changed:
- create_credentials_file: true (was false)
- export_environment_variables: true (was false)

This allows the google-github-actions/auth action to create the credential
file and set GOOGLE_APPLICATION_CREDENTIALS so Claude can access it.

Author: rafabene

.github/workflows/open-prs-digest.yml

@@ -68,8 +68,8 @@ jobs:
         uses: google-github-actions/auth@7c6bc770dae815cd3e89ee6cdf493a5fab2cc093 # v3.0.0
         with:
           credentials_json: ${{ secrets.GCP_SA_KEY }}
-          create_credentials_file: false
-          export_environment_variables: false
+          create_credentials_file: true
+          export_environment_variables: true
 
       - name: Resolve dynamic context in SKILL.md
         run: |