feat: port session 19 — JetStream Core

- JetStreamTypes: JetStreamConfig, JetStreamStats, JetStreamAccountLimits,
  JetStreamTier, JetStreamAccountStats, JetStream engine, JsAccount, JsaUsage
- JetStreamApiTypes: 50+ JSApi request/response types, API subject constants
- JetStreamErrors: JsApiError + JsApiErrors with all 203 error codes
- JetStreamVersioning: version constants and API level helpers
- JetStreamBatching: Batching, BatchGroup, BatchStagedDiff, BatchApply
- Removed JetStreamConfig/JetStreamState stubs from NatsServerTypes.cs
- 374 features complete (IDs 1368-1519, 1751-1972)

dotnet/src/ZB.MOM.NatsNet.Server/JetStream/JetStreamBatching.cs

@@ -0,0 +1,132 @@
+// Copyright 2025 The NATS Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Adapted from server/jetstream_batching.go in the NATS server Go source.
+
+namespace ZB.MOM.NatsNet.Server;
+
+// ---------------------------------------------------------------------------
+// Batching types
+// ---------------------------------------------------------------------------
+
+/// <summary>
+/// Tracks in-progress atomic publish batch groups for a stream.
+/// Mirrors the <c>batching</c> struct in server/jetstream_batching.go.
+/// </summary>
+internal sealed class Batching
+{
+    private readonly Lock _mu = new();
+    private readonly Dictionary<string, BatchGroup> _group = new(StringComparer.Ordinal);
+
+    public Lock Mu    => _mu;
+    public Dictionary<string, BatchGroup> Group => _group;
+}
+
+/// <summary>
+/// A single in-progress atomic batch: its temporary store and cleanup timer.
+/// Mirrors <c>batchGroup</c> in server/jetstream_batching.go.
+/// </summary>
+internal sealed class BatchGroup
+{
+    /// <summary>Last proposed stream sequence for this batch.</summary>
+    public ulong  LastSeq { get; set; }
+
+    /// <summary>Temporary backing store for the batch's messages.</summary>
+    public object? Store  { get; set; }  // IStreamStore — session 20
+
+    /// <summary>Timer that abandons the batch after the configured timeout.</summary>
+    public Timer? BatchTimer { get; set; }
+
+    /// <summary>
+    /// Stops the cleanup timer and flushes pending writes so the batch is
+    /// ready to be committed.
+    /// Mirrors <c>batchGroup.readyForCommit</c>.
+    /// </summary>
+    public bool ReadyForCommit()
+    {
+        // Stub — full implementation requires IStreamStore.FlushAllPending (session 20).
+        return BatchTimer?.Change(Timeout.Infinite, Timeout.Infinite) != null;
+    }
+}
+
+/// <summary>
+/// Stages consistency-check data for a single atomic batch before it is committed.
+/// Mirrors <c>batchStagedDiff</c> in server/jetstream_batching.go.
+/// </summary>
+internal sealed class BatchStagedDiff
+{
+    /// <summary>Message IDs seen in this batch, for duplicate detection.</summary>
+    public Dictionary<string, object?>? MsgIds             { get; set; }
+
+    /// <summary>Running counter totals, keyed by subject.</summary>
+    public Dictionary<string, object?>? Counter            { get; set; }  // map[string]*msgCounterRunningTotal
+
+    /// <summary>Inflight subject byte/op totals for DiscardNew checks.</summary>
+    public Dictionary<string, object?>? Inflight           { get; set; }  // map[string]*inflightSubjectRunningTotal
+
+    /// <summary>Expected-last-seq-per-subject checks staged in this batch.</summary>
+    public Dictionary<string, BatchExpectedPerSubject>? ExpectedPerSubject { get; set; }
+}
+
+/// <summary>
+/// Cached expected-last-sequence-per-subject result for a single subject within a batch.
+/// Mirrors <c>batchExpectedPerSubject</c> in server/jetstream_batching.go.
+/// </summary>
+internal sealed class BatchExpectedPerSubject
+{
+    /// <summary>Stream sequence of the last message on this subject at proposal time.</summary>
+    public ulong SSeq  { get; set; }
+
+    /// <summary>Clustered proposal sequence at which this check was computed.</summary>
+    public ulong ClSeq { get; set; }
+}
+
+/// <summary>
+/// Tracks the in-progress application of a committed batch on the Raft apply path.
+/// Mirrors <c>batchApply</c> in server/jetstream_batching.go.
+/// </summary>
+internal sealed class BatchApply
+{
+    private readonly Lock _mu = new();
+
+    /// <summary>ID of the current batch.</summary>
+    public string    Id          { get; set; } = string.Empty;
+
+    /// <summary>Number of entries expected in the batch (for consistency checks).</summary>
+    public ulong     Count       { get; set; }
+
+    /// <summary>Raft committed entries that make up this batch.</summary>
+    public List<object?>? Entries { get; set; }  // []*CommittedEntry — session 20+
+
+    /// <summary>Index within an entry indicating the first message of the batch.</summary>
+    public int       EntryStart  { get; set; }
+
+    /// <summary>Applied value before the entry containing the first batch message.</summary>
+    public ulong     MaxApplied  { get; set; }
+
+    public Lock Mu => _mu;
+
+    /// <summary>
+    /// Clears in-memory apply-batch state.
+    /// Mirrors <c>batchApply.clearBatchStateLocked</c>.
+    /// Lock should be held.
+    /// </summary>
+    public void ClearBatchStateLocked()
+    {
+        Id         = string.Empty;
+        Count      = 0;
+        Entries    = null;
+        EntryStart = 0;
+        MaxApplied = 0;
+    }
+}