Bundle should-refuse sweep data for Calibration tab

Add Calibration tab: PC-tier scatter + TPR bars from should-refuse sweep

Redesign UI: theme-aware leaderboard, thesis-forward hero, cleaner cells

Redesign leaderboard: two-row header, heatmap tints, progress bars, rank column, intro blurb

Fix sdk_version to 5.50.0 (exact release required by HF)

Deploy RefusalBench leaderboard (v1.1-frozen, arXiv:2605.21545)

Deploy RefusalBench leaderboard (v1.1-frozen, arXiv:2605.21545)

initial commit