code-v6.4

Corrected reference implementation of the HCMA brain (v6.4). Applies four audit-driven fidelity fixes ([F1]–[F4]) with zero behavioral change on the published benchmark: 100/100 parity across 5 domains × 4 tiers, and an unchanged frozen spec hash (a0258b10…). [F1] version collapse = max(transaction_time) [F2] order-independent negative voting [F3] full-state tamper-evidence + deep_sleep state verification [F4] physical compaction of tombstones (right to be forgotten / GDPR Art. 17) Includes: hcma_v64.py, the deterministic regression guard (audit_brain_repro.py), limitations & erasure notes (paper1_limitations.md), the version manifest (README_VERSIONS.txt), and the Claude Sonnet consultation records. v6.3 (hcma_v6.py) remains the frozen, published baseline.