fix(ci): replace auto-commit with build staleness check

[ngjinshan]

The aws-samples repo doesn't allow github-actions[bot] to push. CI now rebuilds from src/ and fails if the committed configurator.html doesn't match, with instructions to run 'npm run build'.

Description

Brief description of the change and the problem it solves.

Type of change

• Bug fix
• New resource type support
• Security improvement
• Documentation update

Testing

• Tested end-to-end in a real AWS account (or CI E2E will cover this)
• No false positives observed
• CloudWatch logs reviewed for errors

Checklist

• CloudFormation template is valid (cfn-lint passes — checked by CI)
• IAM permissions follow least-privilege (only tag actions added)
• If adding a new service handler: corresponding resource added to .github/scripts/resource_groups/ for E2E coverage
• CHANGELOG.md updated

CI Notes

Layer 1 (lint) runs immediately on every PR — ~1 min.
Layer 2 (E2E) runs when configurator.yaml or configurator.html changes — ~37 min across 7 AWS accounts. No AWS credentials needed.
If Layer 2 fails, download verification-report.json from the Actions run for details.