Why: the migration safety net (archive refs, bundles, SHA maps) had never
been exercised; verification rules treat untested recovery as a claim.
Evidence: 15/15 drill checks in a remote-only fresh environment (fsck, tip
and count matches, go test passing on the restored pre-rewrite tip, parent
gitlink reachability); the found gap — chain SHAs only in local bundles —
fixed by pushing refs/rewrite-backup/pre-2026-09-30-chain.
Impact: record-only; backend full-chain restore noted as a known, accepted
limitation.
Refs: 2026-09-30-history-migration.md; 2026-09-30-history-migration-sha-map.md
weichen