Closes the two deferred deep campaigns from 6D on live infra: tier-2 v2 layout
engine (A1-A4) and F7 atomic-write + restic C2 self-heal (B1-B4). No production
code shipped. Two LOW findings (F-6E-1 demo drive drift; T-6E-1 DB-dump dir-fsync
parity). Drill repo torn down; fixtures reverted; box healthy.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HEPuEwyyGDJdcsXLFsTWJn
