docs(runbooks): flatKV↔memIAVL parity via sharded historical replay

.agent/runbooks/README.md

@@ -31,6 +31,7 @@ Agents fetch this `README.md` to discover what's available, then `WebFetch` the
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 | [`operating-archive-node-byov.md`](operating-archive-node-byov.md) | Required volume contents, PV/PVC spec, SeiNode/SeiNetwork spec, controller validation surface, and EBS-swap cutover sequence for archive nodes using the bring-your-own-volume (`dataVolume.import`) path. | Bringing up an archive node from a pre-populated EBS; swapping the underlying volume of an existing archive PV; debugging `ImportPVCReady=False`; receipt-store pruning concerns. |
 | [`migrating-validator-to-byo-secrets.md`](migrating-validator-to-byo-secrets.md) | Cutting a live validator from a legacy host onto the platform carrying its consensus identity via Secrets (`signingKey`/`nodeKey`): what migrates, SeiNetwork spec, controller validation surface, the stop-before-start double-sign discipline + layered equivocation defenses, cutover/rollback sequence, and dry-run gotchas. | Migrating an existing validator (e.g. arctic-1 node-19) off EC2 onto K8s; any cutover where a consensus key changes hosts; understanding the `replicas:1` CEL guard or the double-sign alerts. |
+| [`validating-flatkv-memiavl-parity-via-sharded-replay.md`](validating-flatkv-memiavl-parity-via-sharded-replay.md) | flatKV↔memIAVL storage-engine parity validation by differential historical replay: the flatKV+memIAVL replay-pair topology (same binary, same snapshot, blocks from a shared archive), the correctness gates (compare pair-not-archive; verify migration complete so flatKV reads are genuine; `historical_replay` build for pre-v6.5 txs), the seictl shadow comparator, result aggregation + Notion report, and the fan-out to 50+ shards. | Standing up a flatKV-vs-memIAVL correctness validation on harbor; driving a sharded replay campaign; debugging why a replay node is stuck or a comparison reads all-indeterminate/vacuous; understanding `migrate_evm` vs `memiavl_only`/`evm_migrated`/`flatkv_only` read routing. |
 
 ## Adding a new runbook