feat: initialize project structure and error types

- go.mod with github.com/dailz/go-kv, Go 1.26.3, testify
- config/config.go with WalConfig, Validate() with checked arithmetic
- errors.go with sentinel errors (ErrCommitUnknown, ErrWriteStopped, etc.)
- wal/constants.go with all WAL format constants and enums
- wal/header.go with WAL File Header encode/decode (CRC32 IEEE)
- wal/record.go with Physical Record codec, block boundary, SplitIntoRecords
- wal/entry.go with WAL Entry codec (varint keys/values, OpType, ValueKind)
- wal/sequence.go with SequenceManager (atomic, CAS, overflow-safe)
- manifest/manifest.go with MANIFEST stub (Load/Save atomic)
- manifest/current.go with CURRENT file (WriteCurrent/ReadCurrent)
- Comprehensive tests for all modules
- .golangci.yml configuration

.omo/run-continuation/ses_149f503d8ffeCitCeNNhuI5uPD.json

@@ -0,0 +1,10 @@
+{
+  "sessionID": "ses_149f503d8ffeCitCeNNhuI5uPD",
+  "updatedAt": "2026-06-11T09:38:47.486Z",
+  "sources": {
+    "background-task": {
+      "state": "idle",
+      "updatedAt": "2026-06-11T09:38:47.486Z"
+    }
+  }
+}