Integrate reproducible Day 2 engineering workflow

[hjjjs4vbmv-netizen]

Summary

• Add reproducible MatPool environment setup and validation
• Add CIFAR-10 dataset and EDM checkpoint integrity checks
• Add an engineering-only AMP/GradScaler smoke workflow
• Standardize persistent paths under /mnt/ect_project
• Add Day 2 collaborator audit and integration reports

Scope

This PR contains one Day 2 engineering integration commit based on the merged Day 1 baseline.

It does not modify:

• ct_train.py
• training/ct_training_loop.py
• env.yml
• .gitignore
• README.md

The verified Day 1 AMP, GradScaler, checkpoint-resume, and metrics=none behavior is preserved from main.

Validation

• Shell syntax checks: PASS
• Python compileall: PASS
• Environment validation in ect: PASS
• CIFAR-10 check-only: PASS
• EDM checkpoint check-only: PASS
• Engineering smoke check-only: PASS
• AMP/GradScaler dry-run: PASS
• Git diff check: PASS

No real training, full smoke run, FID, or KID was performed.

Commit

36dcae6f5416b2e1be770e70f6f81a20b2d2cb6b