ci: use GitHub App client ID input

Update actions/create-github-app-token@v3 usage in the libvhdi tag-release job from the deprecated app-id input to client-id. The workflow now expects UPDATE_GITHUB_APP_CLIENT_ID plus UPDATE_GITHUB_APP_PRIVATE_KEY.

Validation: git diff --check; grep confirmed no remaining app-id or UPDATE_GITHUB_APP_ID references. Local actionlint still reports stale metadata that requires app-id, but the live v3 action and GitHub runner warning require client-id.

Author: declarative-dale

.github/workflows/ci.yml

@@ -79,7 +79,7 @@ jobs:
         continue-on-error: true
         uses: actions/create-github-app-token@v3
         with:
-          app-id: ${{ vars.UPDATE_GITHUB_APP_ID }}
+          client-id: ${{ vars.UPDATE_GITHUB_APP_CLIENT_ID }}
           private-key: ${{ secrets.UPDATE_GITHUB_APP_PRIVATE_KEY }}
           permission-contents: write
           permission-workflows: write
@@ -153,7 +153,7 @@ jobs:
               echo "Automatic libvhdi version tagging skipped because GitHub App token creation failed."
               echo ""
               echo "Configure the GitHub App credentials before rerunning this workflow:"
-              echo "- Variable: \`UPDATE_GITHUB_APP_ID\`"
+              echo "- Variable: \`UPDATE_GITHUB_APP_CLIENT_ID\`"
               echo "- Secret: \`UPDATE_GITHUB_APP_PRIVATE_KEY\`"
             } >> "$GITHUB_STEP_SUMMARY"
           elif [ "${{ steps.detect_tag.outputs.create_tag }}" = "true" ]; then