Agent Skills: review-ownership-map

Review, create, or update a code-ownership and knowledge-risk map (docs/ownership-map.md) from git history — compute bus factor, find single points of failure, flag sensitive files owned by one person, detect CODEOWNERS drift and stale security code. Use when the user wants an ownership map, bus factor / truck factor analysis, knowledge-risk audit, single-point-of-failure review, or ISO 27001 segregation-of-duties / competence evidence. Read-only on code; creates the doc if missing, updates it if present.