Update README with ISO-Bench scope

Update: 594 ISO-Bench benchmarks (vLLM 29/39 + SGLang 10/15 tasks)

Update README with accurate stats (86 rows, no empty/missing data)

Remove image_not_found rows (no benchmark data)

Remove empty_patch rows (no useful data — agent failed to produce patches)

Add dataset README

Add pass@k GPU benchmark results (vLLM, claude_code + codex_cli)

initial commit