grain-confidence-reviewer

Surface grain-uniqueness CONFIDENCE as evidence and DIFF two source-map.yaml versions for a Mapping Ready reviewer in the Seshat BI repo. Use when someone asks "is the grain confident?", "what changed in this map?", or is about to review/approve a table's mapping. It READS the already-measured PK-uniqueness signal (PkProof from profile.py / the committed source-profile.md) and reads two map versions from git, then…