…paction

- pebbleStore: implement Compact() with batched MVCC garbage collection
  that iterates keys, keeps one version <= minTS per user key, and
  deletes older versions in batches of 1000
- pebbleStore: implement RetentionController interface (MinRetainedTS /
  SetMinRetainedTS) so FSMCompactor no longer skips pebbleStore
- mvccStore: split Compact into 2-phase approach — scan under RLock to
  collect candidates, then apply updates in batched Lock/Unlock cycles
  (batch size 500) to avoid blocking all reads/writes during compaction
- docs: update review_todo.md marking completed items

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…ding

- store: add TxnInternalKeyPrefix constant for compaction filtering
- mvccStore/pebbleStore: skip keys with !txn| prefix during Compact()
  to prevent breaking lock resolution by pruning commit/rollback records
- txn_codec: replace bytes.Buffer with direct slice encoding in
  EncodeTxnMeta, encodeTxnLock, encodeTxnIntent to eliminate per-call
  heap allocations
- docs: update review_todo.md marking 1.6 and 3.8 as done, downgrade 1.2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…nsafe

- Fix meta key namespace collision (4.1): prefix with \x00, add backward
  compat migration in findMaxCommitTS, isMetaKey helper for scan/compact
- Add background LockResolver (1.4/2.3): periodically scans expired locks
  on leader nodes and resolves orphaned commit/abort locks
- Add forward retry with limit (2.2): forwardWithRetry re-fetches leader
  address on each failure, bounds retries to 3
- Add decodeKeyUnsafe (3.9): zero-copy key decode for temporary comparisons
  in hot iteration paths (GetAt, ExistsAt, LatestCommitTS, Compact)
- Document Snapshot Isolation (4.2): clarify write-skew limitation in
  handleOnePhaseTxnRequest and MVCCStore.ApplyMutations
- Document cross-shard scan limitation (4.5) and VerifyLeader TOCTOU (4.3)
- Mark DynamoDB ConditionCheck (4.4) as already addressed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…Dispatch

- FSM Abort path (5.1): 10 tests covering Prepare→Abort flow, commit
  rejection, lock/intent cleanup, rollback record, edge cases
- PebbleStore transactions (5.2): 14 tests covering ApplyMutations
  conflict detection, atomic batch, TTL, LatestCommitTS, Compact with
  meta/txn key preservation
- Coordinate.Dispatch (5.3): 6 tests covering raw put/del, one-phase
  txn, validation, and automatic startTS assignment

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- ShardedCoordinator abort (5.4): test verifying that when Shard2 Prepare
  fails, Shard1 receives correct Abort and locks are cleaned up
- Concurrent access (5.6): 7 new race-detected tests covering concurrent
  PutAt, GetAt+PutAt, ApplyMutations, ScanAt+PutAt, and scan snapshot
  consistency for MVCCStore

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…cated prefix bytes

Co-authored-by: bootjp <1306365+bootjp@users.noreply.github.com>
Agent-Logs-Url: https://github.com/bootjp/elastickv/sessions/8c736c29-0405-4197-93a2-8f290254f51d

…rdinator_abort_test.go, and lsm_store.go

Co-authored-by: bootjp <1306365+bootjp@users.noreply.github.com>
Agent-Logs-Url: https://github.com/bootjp/elastickv/sessions/aed61b49-9084-425e-bd0e-899be4c0bf9d

…ction

- kv/fsm.go: extract decodeLegacyRaftRequest from decodeRaftRequests default case
- cmd/server/demo.go: extract setupFSMStore from run function
- store/lsm_store.go: extract compactEntryState/shouldDeleteEntry/compactFlushBatch
  for Compact; extract restoreMVCCEntries for restoreFromStreamingMVCC;
  extract restoreGobEntries for restoreFromLegacyGob; add hash import
- store/mvcc_store.go: lift compactEntry to package scope; extract
  computeScanCapHint/collectScanResults for ScanAt; extract
  compactPhase1/compactPhase2 for Compact
- store/mvcc_store_concurrency_test.go: extract goroutine bodies into
  concurrentGetAtWriter/concurrentGetAtReader, scanAtWriter/scanAtScanner,
  snapshotConsistencyWriter/snapshotConsistencyScanner helpers
- kv/lock_resolver.go: fix pre-existing undefined ok/userKey variables by
  using txnUserKeyFromLockKey; apply gofmt alignment

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

…etypeassert, wrapcheck, mnd, gosec, unused)

Co-authored-by: bootjp <1306365+bootjp@users.noreply.github.com>
Agent-Logs-Url: https://github.com/bootjp/elastickv/sessions/aed61b49-9084-425e-bd0e-899be4c0bf9d

fix: correct Pebble iterator bounds and use pre-allocated txn prefix bytes