Add collaborative notebook reproducibility guard

[jtc268]

/claim #12

Summary

• Adds collab-notebook-reproducibility-guard/, a focused issue Real-time collaborative research editor & interface #12 slice for embedded Jupyter-style notebook outputs in the real-time collaborative research editor.
• Gates notebook output packets before shared manuscript acceptance using execution-order continuity, kernel/runtime fingerprints, dependency lock hashes, random seed capture, input artifact fingerprints, stale output timestamps, untrusted rich HTML, private local paths, and section-version drift.
• Emits deterministic accept/review/hold lanes, reviewer actions, SHA-256 audit digests, JSON packets, Markdown/SVG reports, and a short MP4 demo built from synthetic data.

Non-overlap

This is scoped to notebook output reproducibility before collaborative manuscript insertion. It does not duplicate the broad editor foundation, operation replay, offline conflict, notebook kernel lease, autosave/local-cache privacy, reference merge, data availability, LaTeX macro safety, suggestion provenance, clipboard/import provenance, presence liveness, accessibility, evidence binding, embargo release, notification visibility, review decision, or task dependency slices.

Validation

• node collab-notebook-reproducibility-guard/test.js
• npm test from collab-notebook-reproducibility-guard/
• npm run demo from collab-notebook-reproducibility-guard/
• npm run video from collab-notebook-reproducibility-guard/
• npm run check from collab-notebook-reproducibility-guard/
• ffprobe verified collab-notebook-reproducibility-guard/reports/demo.mp4 as H.264, 960x540, 9.0s, 88432 bytes
• git diff --cached --check
• git diff --check

No external services, credentials, private manuscripts, live collaborator data, or payout data are used.