Replaced curated 50-question subset with complete toxigen/toxigen-data
(annotated split). 27 target groups, rich metadata (intent, framing,
stereotyping, factual, lewd, toxicity_human, toxicity_ai).

9,900 prompts × 8 rounds × 2 models = 158,400 data points for the
silent exit research. Each prompt carries its target_group for
per-category refusal rate analysis.

Also fixes samples_start wrap-around for continuous farming.

Co-Authored-By: Virgil <virgil@lethean.io>