Add knowledge graph evidence freshness

[HunterCML]

@algora-pbc /claim #17

Summary

• add a focused knowledge-graph evidence freshness module for Scientific Knowledge Graph Integration
• score evidence freshness risks from retractions, corrections, supersession, stale age, failed replication, and missing evidence
• suppress unsafe graph recommendations, route corrected/stale edges to review, and surface replacement evidence candidates for entity pages

Demo Evidence

• Included knowledge-graph-evidence-freshness/demo.mp4 as the required short video artifact.
• Included knowledge-graph-evidence-freshness/demo.svg, requirements-map.md, and acceptance-notes.md for reviewer context.

Validation

• node knowledge-graph-evidence-freshness/test.js
• node knowledge-graph-evidence-freshness/demo.js
• git diff --check