v0.5.1

Fixed

• Added durable recovery coverage for NoKV-style metadata stores using many
  named families and multi-family DB::atomic batches under
  Durability::StateMachine.
• Verified that DB::commit_durable(applied_index) can reopen a
  metadata-service-shaped checkpoint without a Holt WAL and retain the durable
  applied index needed for external-log replay.

Validation

• cargo test --test sm_durable durable_recovers_metadata_store_shaped_workload -- --exact --nocapture
• cargo test --release --test sm_durable durable_recovers_metadata_store_shaped_workload -- --exact
• NoKV sibling validation with a local Holt patch:
  cargo test --config 'patch.crates-io.holt.path="../holt"' -p nokv-meta -p nokv-cluster -p nokv-server