Add dataset schema evolution gate

[codeaustral-oss]

Summary

• Adds a self-contained dataset schema evolution compatibility gate for Scientific/Engineering Data & Code Hosting.
• Compares hosted dataset schema versions for renamed fields, breaking type/unit/identifier drift, nullability changes, and added fields.
• Decides whether previews, API consumers, and executable reruns remain compatible, then emits reviewer actions plus DataCite/schema.org metadata updates.
• Includes JSON, Markdown, SVG, and short MP4 demo artifacts.

Scope

This focuses on dataset schema evolution compatibility for #14 and avoids overlapping with existing FAIR manifest, artifact package integrity, preview cache, raw-instrument preview, notebook preview, retention/tombstone, model-card lineage, license compatibility, sensitive-redaction, environment drift, provenance-chain, quarantine/rerun, quota/dedup, and access-gate slices.

Verification

• node dataset-schema-evolution-gate/test.js
• node dataset-schema-evolution-gate/demo.js
• node --check dataset-schema-evolution-gate/index.js
• node --check dataset-schema-evolution-gate/sample-data.js
• node --check dataset-schema-evolution-gate/test.js
• node --check dataset-schema-evolution-gate/demo.js
• ffprobe -v error -show_entries format=duration,size -show_entries stream=codec_name,width,height -of default=noprint_wrappers=1 dataset-schema-evolution-gate/reports/demo.mp4
• git diff --check

/claim #14