Add execution environment drift governance

[FeeeeelixWong]

Summary

• Add a self-contained execution environment drift governance module for Scientific/Engineering Data & Code Hosting (Scientific/Engineering Data & Code Hosting #14).
• Fingerprint artifact capsules and runtime environments, detect dependency/base-image/GPU/network drift, and plan scheduled reruns with RUN_NOW/REVIEW_REQUIRED/BLOCKED decisions.
• Generate FAIR/JSON-LD/DataCite export evidence, retention/embargo decisions, a requirement map, sample data, tests, demo packet, and a short mp4 demo artifact.

Demo

• execution-environment-drift-governance/demo/execution-drift-governance-demo.mp4
• execution-environment-drift-governance/demo/execution-drift-governance-packet.json

Verification

• npm test -> 7 tests passed
• npm run demo -> generated governance packet with 3 artifacts, 2 ready artifacts, 1 blocked artifact, 1 runnable rerun, and 1 blocked rerun
• ffprobe -v error -select_streams v:0 -show_entries stream=codec_name,width,height,duration -of default=nokey=1:noprint_wrappers=1 execution-environment-drift-governance/demo/execution-drift-governance-demo.mp4 -> h264, 1280x720, 6.000000s
• git diff --check -> passed

/claim #14
@algora-pbc /claim #14