Add agent-shadow-brain to Machine Learning software

[theihtisham]

Summary

• Adds agent-shadow-brain to the Software > Machine Learning section
• Background code analysis engine using neural mesh architecture, pattern memory, and ML-driven insights for automated code quality assessment and anomaly detection
• Follows the contribution link template format

Checklist

• Follows link template: [Title](URL) - Description.
• Correctly classified as Software > Machine Learning
• Not a duplicate
• Description does not start with "A" or "The"
• Commit signed off (DCO)