Add chemical identity stereochemistry guard

[AlonePenguin]

@algora-pbc /claim #17
/claim #17

Summary

• Adds chemical-identity-stereochemistry-guard/, a dependency-free chemical identity and stereochemistry gate for SCIBASE knowledge graph compound nodes and edges.
• Validates InChIKey format, isomeric SMILES presence, required stereochemistry, salt/hydrate form conflation, isotope-label metadata, DOI-backed identity evidence, synonym collisions, same_as edge safety, assay-context completeness, and relationship evidence.
• Includes clean/risky synthetic fixtures, deterministic tests, JSON/Markdown reports, an SVG dashboard, and a committed MP4 demo artifact.

Issue Fit

This is scoped to Scientific Knowledge Graph Integration issue #17 and is distinct from existing broad extraction/navigation, ontology drift/aliases, biological accession crosswalks, measurement harmonization, geospatial provenance, sample custody/cold-chain, protocol deviation/reagent lot checks, software dependency provenance, image metadata, funding provenance, temporal consistency, and recommendation visibility/diversity slices. It focuses specifically on chemical identity and stereochemistry before graph merge or recommendation publication.

Validation

npm --prefix chemical-identity-stereochemistry-guard run check
npm --prefix chemical-identity-stereochemistry-guard run demo
npm --prefix chemical-identity-stereochemistry-guard run make-demo-video
npm --prefix chemical-identity-stereochemistry-guard run verify-video

Observed locally:

chemical identity stereochemistry guard tests passed
Wrote chemical identity stereochemistry guard reports:
- chemical-identity-stereochemistry-guard/reports/clean-chemical-identity-report.json
- chemical-identity-stereochemistry-guard/reports/risky-chemical-identity-report.json
- chemical-identity-stereochemistry-guard/reports/risky-chemical-identity-handoff.md
- chemical-identity-stereochemistry-guard/reports/chemical-identity-dashboard.svg
Wrote chemical-identity-stereochemistry-guard/reports/demo.mp4
demo.mp4 verified: h264, 960x540, 4.000s, 18/1

[AlonePenguin]

@algora-pbc /claim #17

Claiming issue #17 for PR #560. The PR body already includes both @algora-pbc /claim #17 and /claim #17, plus local validation output and the committed demo MP4.