chore: add changeset for 0.8.0 correctness fixes

.changeset/correctness-fixes-0-8-0.md

@@ -0,0 +1,53 @@
+---
+'@kafkats/client': patch
+'@kafkats/flow': patch
+'@kafkats/codec-zod': patch
+'@kafkats/flow-state-lmdb': patch
+---
+
+Correctness and reliability fixes across the producer, consumer, client protocol, and flow state stores.
+
+### Producer
+
+- `flush()` now waits for deferred drains so it no longer resolves while writes are still buffered.
+- `transactionalSend` freezes its partition set up front to avoid double-calling the partitioner.
+- Retry `TxnOffsetCommit` on retriable and rebalance-in-progress errors instead of failing the transaction.
+- Fence the producer on `OUT_OF_ORDER_SEQUENCE_NUMBER` to surface the idempotence violation rather than silently corrupting the stream.
+- Reject orphaned in-flight send promises during disconnect so callers are not left hanging.
+
+### Consumer
+
+- Always reschedule the heartbeat after non-fatal errors, preventing the consumer from dropping out of the group.
+- Surface auto-commit errors to the consumer instead of swallowing them.
+- Clear only the successfully committed partitions on a partial commit failure so the rest are retried.
+- Fence stale fetch responses across partition replacement to avoid delivering records from a revoked assignment.
+
+### Client / protocol
+
+- Guard against varint shift overflow in the decoder.
+- Close a `ConnectionPool.acquire` race that could hand out a connection mid-teardown.
+- Clamp the SASL reauthentication delay to the `setTimeout` maximum.
+- Don't await a response on `Produce` with `acks=0` (the broker sends none).
+- Always use the v0 response header for `ApiVersions`, matching broker behavior across versions.
+
+### Share consumer
+
+- Release (rather than acknowledge) the last yielded message on shutdown so unprocessed records are redelivered.
+
+### Flow
+
+- Write to the local store before the changelog (local-first ordering) to shrink the inconsistency window on crash.
+- Serialize the EOS commit triggered by a rebalance against the next message, and close the EOS rebalance offset-commit gap via an awaitable rebalance hook (shared with the consumer fix above).
+- Use stream time (not wall-clock time) for window expiry.
+- Implement hopping windows (`TimeWindows.advanceBy`).
+- Throw on `SlidingWindows` instead of silently misbehaving (not yet implemented).
+- Correct `TableGroupByNode` mapping ordering.
+- Apply retention to `reduce` and session aggregators, emitting changelog tombstones for expired state.
+- Surface checkpoint persistence errors instead of swallowing them.
+
+### flow-state-lmdb
+
+- Make `range()` upper bound inclusive, matching the in-memory store.
+- Await `fsync` on checkpoint writes so a checkpoint is durable before it is reported complete.
+- Correct `WindowStore` time-bound math.
+- Use order-preserving signed-i64 encoding for time keys so range scans iterate in correct chronological order.