Novelty / anti-duplication guard

A guardrail that blocks the self-improvement and idea loops from shipping changes or ontology concepts that duplicate or near-duplicate ones already shipped, enforcing the doctrine's 'never repeat' rule.

grounded in: doctrine principles.md: 'never repeat or near-duplicate a change already shipped' / 'No duplicate or near-duplicate changes'; enforced by idea_engine.py + ontology_maintain.py