refactor: extract NATS.Server.JetStream.Tests project

Move 225 JetStream-related test files from NATS.Server.Tests into a
dedicated NATS.Server.JetStream.Tests project. This includes root-level
JetStream*.cs files, storage test files (FileStore, MemStore,
StreamStoreContract), and the full JetStream/ subfolder tree (Api,
Cluster, Consumers, MirrorSource, Snapshots, Storage, Streams).

Updated all namespaces, added InternalsVisibleTo, registered in the
solution file, and added the JETSTREAM_INTEGRATION_MATRIX define.

tests/NATS.Server.JetStream.Tests/JetStream/Consumers/ConsumerPauseResumeTests.cs

@@ -0,0 +1,103 @@
+using NATS.Server.JetStream;
+using NATS.Server.JetStream.Models;
+
+namespace NATS.Server.JetStream.Tests.JetStream.Consumers;
+
+/// <summary>
+/// Tests for consumer pause/resume with auto-resume timer.
+/// Go reference: consumer.go (pause/resume).
+/// </summary>
+public class ConsumerPauseResumeTests
+{
+    private static ConsumerManager CreateManager() => new();
+
+    private static void CreateConsumer(ConsumerManager mgr, string stream, string name)
+    {
+        mgr.CreateOrUpdate(stream, new ConsumerConfig { DurableName = name });
+    }
+
+    [Fact]
+    public void Pause_with_deadline_sets_paused()
+    {
+        var mgr = CreateManager();
+        CreateConsumer(mgr, "test-stream", "test-consumer");
+
+        var until = DateTime.UtcNow.AddSeconds(5);
+        mgr.Pause("test-stream", "test-consumer", until);
+
+        mgr.IsPaused("test-stream", "test-consumer").ShouldBeTrue();
+        mgr.GetPauseUntil("test-stream", "test-consumer").ShouldBe(until);
+    }
+
+    [Fact]
+    public void Resume_clears_pause()
+    {
+        var mgr = CreateManager();
+        CreateConsumer(mgr, "test-stream", "test-consumer");
+
+        mgr.Pause("test-stream", "test-consumer", DateTime.UtcNow.AddSeconds(5));
+        mgr.Resume("test-stream", "test-consumer");
+
+        mgr.IsPaused("test-stream", "test-consumer").ShouldBeFalse();
+        mgr.GetPauseUntil("test-stream", "test-consumer").ShouldBeNull();
+    }
+
+    [Fact]
+    public async Task Pause_auto_resumes_after_deadline()
+    {
+        var mgr = CreateManager();
+        CreateConsumer(mgr, "test-stream", "test-consumer");
+
+        // Use a semaphore to synchronize on the actual timer callback rather than a blind delay.
+        using var resumed = new SemaphoreSlim(0, 1);
+        mgr.OnAutoResumed += (_, _) => resumed.Release();
+
+        mgr.Pause("test-stream", "test-consumer", DateTime.UtcNow.AddMilliseconds(100));
+
+        var signalled = await resumed.WaitAsync(TimeSpan.FromSeconds(5));
+        signalled.ShouldBeTrue("auto-resume timer did not fire within 5 seconds");
+
+        mgr.IsPaused("test-stream", "test-consumer").ShouldBeFalse();
+    }
+
+    [Fact]
+    public void IsPaused_returns_false_for_unknown_consumer()
+    {
+        var mgr = CreateManager();
+        mgr.IsPaused("unknown", "unknown").ShouldBeFalse();
+    }
+
+    [Fact]
+    public void GetPauseUntil_returns_null_for_unknown_consumer()
+    {
+        var mgr = CreateManager();
+        mgr.GetPauseUntil("unknown", "unknown").ShouldBeNull();
+    }
+
+    [Fact]
+    public void Resume_returns_false_for_unknown_consumer()
+    {
+        var mgr = CreateManager();
+        mgr.Resume("unknown", "unknown").ShouldBeFalse();
+    }
+
+    [Fact]
+    public void Pause_returns_false_for_unknown_consumer()
+    {
+        var mgr = CreateManager();
+        mgr.Pause("unknown", "unknown", DateTime.UtcNow.AddSeconds(5)).ShouldBeFalse();
+    }
+
+    [Fact]
+    public void IsPaused_auto_resumes_expired_deadline()
+    {
+        var mgr = CreateManager();
+        CreateConsumer(mgr, "test-stream", "c1");
+
+        // Pause with a deadline in the past
+        mgr.Pause("test-stream", "c1", DateTime.UtcNow.AddMilliseconds(-100));
+
+        // IsPaused should detect the expired deadline and auto-resume
+        mgr.IsPaused("test-stream", "c1").ShouldBeFalse();
+    }
+}