feat: complete final jetstream parity transport and runtime baselines

src/NATS.Server/Raft/RaftRpcContracts.cs

@@ -10,3 +10,9 @@ public sealed class VoteResponse
 {
     public bool Granted { get; init; }
 }
+
+public sealed class AppendResult
+{
+    public string FollowerId { get; init; } = string.Empty;
+    public bool Success { get; init; }
+}