Add data dictionary release gate

[zergzorg]

Summary

• Adds a self-contained data-dictionary-release-gate/ module for SCIBASE issue Scientific/Engineering Data & Code Hosting #14.
• Evaluates dataset release readiness across column coverage, data dictionary entries, measurement units, missingness explanations, semantic tags, checksums, license/access policy, DataCite, schema.org, and sensitive-variable handling.
• Generates reviewer-ready JSON, Markdown, SVG, and MP4 demo artifacts from synthetic data only.

Non-overlap

This slice focuses on data dictionary and unit readiness before dataset release. It intentionally avoids duplicating existing issue #14 work on license compatibility, sensitive-file redaction, schema evolution, artifact previews/cache, retention tombstones, model-card lineage, and raw instrument preview integrity.

Validation

• npm --prefix data-dictionary-release-gate run check
• npm --prefix data-dictionary-release-gate test
• npm --prefix data-dictionary-release-gate run demo
• ffprobe -v error -show_entries format=duration,size -show_entries stream=codec_name,width,height -of default=noprint_wrappers=1 data-dictionary-release-gate/reports/demo.mp4
• git diff --check

Demo video: data-dictionary-release-gate/reports/demo.mp4

AI-assisted with OpenAI Codex; reviewed and validated locally before submission.

/claim #14