Add --yaml output format option

[carpalsgrabby]

Summary

The script supports human-readable output and JSON. Some users prefer YAML for tool integrations or configuration files.

Proposal

• Add --yaml flag.
• Use PyYAML if available, fall back to error message otherwise.
• Make JSON/YAML mutually exclusive with human output.

Benefit

Improves integration with devops, config tools, and research pipelines.