migrate-workflow-ec2-to-osdc

MEDIUM W012: Unverifiable external dependency detected (runtime URL that controls agent).

• Potentially malicious external URL detected (high risk: 0.90). The workflow documentation shows the OSDC jobs pull and run container images from ghcr.io at runtime (ghcr.io/pytorch/${docker-image-name}${ci-docker-hash ? '-' + ci-docker-hash : ''}), which fetches and executes remote code as a required dependency for the OSDC path.