feat: complete final jetstream parity transport and runtime baselines

src/NATS.Server/Raft/RaftLog.cs

@@ -27,6 +27,36 @@ public sealed class RaftLog
         _entries.Clear();
         _baseIndex = snapshot.LastIncludedIndex;
     }
+
+    public async Task PersistAsync(string path, CancellationToken ct)
+    {
+        Directory.CreateDirectory(Path.GetDirectoryName(path)!);
+        var model = new PersistedLog
+        {
+            BaseIndex = _baseIndex,
+            Entries = [.. _entries],
+        };
+        await File.WriteAllTextAsync(path, System.Text.Json.JsonSerializer.Serialize(model), ct);
+    }
+
+    public static async Task<RaftLog> LoadAsync(string path, CancellationToken ct)
+    {
+        var log = new RaftLog();
+        if (!File.Exists(path))
+            return log;
+
+        var json = await File.ReadAllTextAsync(path, ct);
+        var model = System.Text.Json.JsonSerializer.Deserialize<PersistedLog>(json) ?? new PersistedLog();
+        log._baseIndex = model.BaseIndex;
+        log._entries.AddRange(model.Entries);
+        return log;
+    }
+
+    private sealed class PersistedLog
+    {
+        public long BaseIndex { get; set; }
+        public List<RaftLogEntry> Entries { get; set; } = [];
+    }
 }
 
 public sealed record RaftLogEntry(long Index, int Term, string Command);