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

src/NATS.Server/JetStream/Api/JetStreamApiResponse.cs

@@ -9,7 +9,9 @@ public sealed class JetStreamApiResponse
     public JetStreamConsumerInfo? ConsumerInfo { get; init; }
     public JetStreamAccountInfo? AccountInfo { get; init; }
     public IReadOnlyList<string>? StreamNames { get; init; }
+    public IReadOnlyList<JetStreamStreamInfo>? StreamInfoList { get; init; }
     public IReadOnlyList<string>? ConsumerNames { get; init; }
+    public IReadOnlyList<JetStreamConsumerInfo>? ConsumerInfoList { get; init; }
     public JetStreamStreamMessage? StreamMessage { get; init; }
     public JetStreamDirectMessage? DirectMessage { get; init; }
     public JetStreamSnapshot? Snapshot { get; init; }
@@ -17,6 +19,17 @@ public sealed class JetStreamApiResponse
     public bool Success { get; init; }
     public ulong Purged { get; init; }
 
+    /// <summary>
+    /// Total count of all items (before pagination). Used by list responses for offset-based pagination.
+    /// Go reference: jetstream_api.go — ApiPaged struct includes Total, Offset, Limit fields.
+    /// </summary>
+    public int PaginationTotal { get; init; }
+
+    /// <summary>
+    /// Requested offset for pagination. Echoed back to client so it can calculate the next page.
+    /// </summary>
+    public int PaginationOffset { get; init; }
+
     /// <summary>
     /// Whether the consumer is currently paused. Populated by pause/resume API responses.
     /// Go reference: server/consumer.go jsConsumerPauseResponse.paused field.
@@ -29,6 +42,123 @@ public sealed class JetStreamApiResponse
     /// </summary>
     public DateTime? PauseUntil { get; init; }
 
+    /// <summary>
+    /// Returns a wire-format object for JSON serialization matching the Go server's
+    /// flat response structure (e.g., config/state at root level for stream responses,
+    /// not nested under a wrapper property).
+    /// </summary>
+    public object ToWireFormat()
+    {
+        if (StreamInfo != null)
+        {
+            if (Error != null)
+                return new { type = "io.nats.jetstream.api.v1.stream_create_response", error = Error };
+            return new
+            {
+                type = "io.nats.jetstream.api.v1.stream_create_response",
+                config = ToWireConfig(StreamInfo.Config),
+                state = ToWireState(StreamInfo.State),
+            };
+        }
+
+        if (ConsumerInfo != null)
+        {
+            if (Error != null)
+                return new { type = "io.nats.jetstream.api.v1.consumer_create_response", error = Error };
+            return new
+            {
+                type = "io.nats.jetstream.api.v1.consumer_create_response",
+                stream_name = ConsumerInfo.StreamName,
+                name = ConsumerInfo.Name,
+                config = ToWireConsumerConfig(ConsumerInfo.Config),
+            };
+        }
+
+        if (Error != null)
+            return new { error = Error };
+
+        if (StreamInfoList != null)
+        {
+            var wireStreams = StreamInfoList.Select(s => new
+            {
+                config = ToWireConfig(s.Config),
+                state = ToWireState(s.State),
+            }).ToList();
+            return new { total = PaginationTotal, offset = PaginationOffset, limit = wireStreams.Count, streams = wireStreams };
+        }
+
+        if (StreamNames != null)
+            return new { total = PaginationTotal, offset = PaginationOffset, limit = StreamNames.Count, streams = StreamNames };
+
+        if (ConsumerInfoList != null)
+        {
+            var wireConsumers = ConsumerInfoList.Select(c => new
+            {
+                stream_name = c.StreamName,
+                name = c.Name,
+                config = ToWireConsumerConfig(c.Config),
+            }).ToList();
+            return new { total = PaginationTotal, offset = PaginationOffset, limit = wireConsumers.Count, consumers = wireConsumers };
+        }
+
+        if (ConsumerNames != null)
+            return new { total = PaginationTotal, offset = PaginationOffset, limit = ConsumerNames.Count, consumers = ConsumerNames };
+
+        if (Purged > 0 || Success)
+            return new { success = Success, purged = Purged };
+
+        return new { success = Success };
+    }
+
+    /// <summary>
+    /// Creates a Go-compatible wire format for StreamConfig.
+    /// Only includes fields the Go server sends, with enums as lowercase strings.
+    /// Go reference: server/stream.go StreamConfig JSON marshaling.
+    /// </summary>
+    private static object ToWireConfig(StreamConfig c) => new
+    {
+        name = c.Name,
+        subjects = c.Subjects,
+        retention = c.Retention.ToString().ToLowerInvariant(),
+        max_consumers = c.MaxConsumers,
+        max_msgs = c.MaxMsgs,
+        max_bytes = c.MaxBytes,
+        max_age = c.MaxAge,
+        max_msgs_per_subject = c.MaxMsgsPer,
+        max_msg_size = c.MaxMsgSize,
+        storage = c.Storage.ToString().ToLowerInvariant(),
+        discard = c.Discard.ToString().ToLowerInvariant(),
+        num_replicas = c.Replicas,
+        duplicate_window = (long)c.DuplicateWindowMs * 1_000_000L,
+        sealed_field = c.Sealed,
+        deny_delete = c.DenyDelete,
+        deny_purge = c.DenyPurge,
+        allow_direct = c.AllowDirect,
+        first_seq = c.FirstSeq,
+    };
+
+    private static object ToWireState(ApiStreamState s) => new
+    {
+        messages = s.Messages,
+        bytes = s.Bytes,
+        first_seq = s.FirstSeq,
+        last_seq = s.LastSeq,
+        consumer_count = 0,
+    };
+
+    private static object ToWireConsumerConfig(ConsumerConfig c) => new
+    {
+        durable_name = string.IsNullOrEmpty(c.DurableName) ? null : c.DurableName,
+        name = string.IsNullOrEmpty(c.DurableName) ? null : c.DurableName,
+        deliver_policy = c.DeliverPolicy.ToString().ToLowerInvariant(),
+        ack_policy = c.AckPolicy.ToString().ToLowerInvariant(),
+        replay_policy = c.ReplayPolicy.ToString().ToLowerInvariant(),
+        ack_wait = (long)c.AckWaitMs * 1_000_000L,
+        max_deliver = c.MaxDeliver,
+        max_ack_pending = c.MaxAckPending,
+        filter_subject = c.FilterSubject,
+    };
+
     public static JetStreamApiResponse NotFound(string subject) => new()
     {
         Error = new JetStreamApiError
@@ -99,6 +229,8 @@ public sealed class JetStreamStreamInfo
 
 public sealed class JetStreamConsumerInfo
 {
+    public string? Name { get; init; }
+    public string? StreamName { get; init; }
     public required ConsumerConfig Config { get; init; }
 }