Fix E2E test gaps and add comprehensive E2E + parity test suites

- Fix pull consumer fetch: send original stream subject in HMSG (not inbox)
  so NATS client distinguishes data messages from control messages
- Fix MaxAge expiry: add background timer in StreamManager for periodic pruning
- Fix JetStream wire format: Go-compatible anonymous objects with string enums,
  proper offset-based pagination for stream/consumer list APIs
- Add 42 E2E black-box tests (core messaging, auth, TLS, accounts, JetStream)
- Add ~1000 parity tests across all subsystems (gaps closure)
- Update gap inventory docs to reflect implementation status

tests/NATS.Server.Tests/Raft/RaftParityBatch3Tests.cs

@@ -0,0 +1,79 @@
+using NATS.Server.Raft;
+
+namespace NATS.Server.Tests.Raft;
+
+public class RaftParityBatch3Tests
+{
+    [Fact]
+    public async Task ProposeMulti_proposes_entries_in_order()
+    {
+        using var leader = ElectSingleNodeLeader();
+
+        var indexes = await leader.ProposeMultiAsync(["cmd-1", "cmd-2", "cmd-3"], CancellationToken.None);
+
+        indexes.Count.ShouldBe(3);
+        indexes[0].ShouldBe(1);
+        indexes[1].ShouldBe(2);
+        indexes[2].ShouldBe(3);
+        leader.Log.Entries.Count.ShouldBe(3);
+    }
+
+    [Fact]
+    public void PeerState_tracks_lag_and_current_flags()
+    {
+        var peer = new RaftPeerState
+        {
+            PeerId = "n2",
+            NextIndex = 10,
+            MatchIndex = 7,
+            LastContact = DateTime.UtcNow,
+        };
+
+        peer.RecalculateLag();
+        peer.RefreshCurrent(TimeSpan.FromSeconds(1));
+
+        peer.Lag.ShouldBe(2);
+        peer.Current.ShouldBeTrue();
+
+        peer.LastContact = DateTime.UtcNow - TimeSpan.FromSeconds(5);
+        peer.RefreshCurrent(TimeSpan.FromSeconds(1));
+        peer.Current.ShouldBeFalse();
+    }
+
+    [Fact]
+    public void CommittedEntry_contains_index_and_entries()
+    {
+        var entries = new[]
+        {
+            new RaftLogEntry(42, 3, "set x"),
+            new RaftLogEntry(43, 3, "set y"),
+        };
+
+        var committed = new CommittedEntry(43, entries);
+
+        committed.Index.ShouldBe(43);
+        committed.Entries.Count.ShouldBe(2);
+        committed.Entries[0].Command.ShouldBe("set x");
+    }
+
+    [Fact]
+    public void RaftEntry_roundtrips_to_wire_shape()
+    {
+        var entry = new RaftEntry(RaftEntryType.AddPeer, new byte[] { 1, 2, 3 });
+
+        var wire = entry.ToWire();
+        var decoded = RaftEntry.FromWire(wire);
+
+        decoded.Type.ShouldBe(RaftEntryType.AddPeer);
+        decoded.Data.ShouldBe(new byte[] { 1, 2, 3 });
+    }
+
+    private static RaftNode ElectSingleNodeLeader()
+    {
+        var node = new RaftNode("n1");
+        node.ConfigureCluster([node]);
+        node.StartElection(1);
+        node.IsLeader.ShouldBeTrue();
+        return node;
+    }
+}