Add scientific image metadata provenance graph guard

[goodgoodclaw]

/claim #17

Summary

• Add a dependency-free scientific image metadata provenance guard for Knowledge Graph image nodes.
• Validate source artifact, dataset, protocol, checksum, acquisition chronology, channel and pixel-size metadata, license, access state, and private identifier leakage before KG publication.
• Emit publish/review/block decisions, safe graph edges, redaction actions, and reviewer-ready JSON/Markdown/SVG demo artifacts.

Verification

• python3 -m unittest scientific-image-metadata-provenance-guard/test_image_metadata_provenance_guard.py
• python3 scientific-image-metadata-provenance-guard/image_metadata_provenance_guard.py --sample --json scientific-image-metadata-provenance-guard/demo/report.json --markdown scientific-image-metadata-provenance-guard/demo/summary.md --svg scientific-image-metadata-provenance-guard/demo/graph.svg
• python3 -m py_compile scientific-image-metadata-provenance-guard/image_metadata_provenance_guard.py scientific-image-metadata-provenance-guard/test_image_metadata_provenance_guard.py
• git diff --check

AI-assisted with Codex; reviewed and verified locally.