Update SkillsBench v1.1 leaderboard copy

card: note the refreshed v1.1 board (15 models / 8 families / 18 configs)

Update README.md

Mirror SkillsBench v1.1 as a benchmark task-tree dataset

Reorganize SkillsBench as v1.1 benchmark dataset

docs: feature as benchmark — arxiv citation, paper teaser, leaderboard cross-link

Update README.md

data: full task corpus @ 05f263429c (91 tasks, full scope)

docs: dataset card for source commit 05f263429c

initial commit