feat: execute full-repo remaining parity closure plan

tests/NATS.Server.Tests/IO/AdaptiveReadBufferTests.cs

@@ -0,0 +1,17 @@
+using NATS.Server.IO;
+
+namespace NATS.Server.Tests;
+
+public class AdaptiveReadBufferTests
+{
+    [Fact]
+    public void Read_buffer_scales_between_512_and_65536_based_on_recent_payload_pattern()
+    {
+        var b = new AdaptiveReadBuffer();
+        b.RecordRead(512);
+        b.RecordRead(4096);
+        b.RecordRead(32000);
+        b.CurrentSize.ShouldBeGreaterThan(4096);
+        b.CurrentSize.ShouldBeLessThanOrEqualTo(64 * 1024);
+    }
+}

tests/NATS.Server.Tests/IO/OutboundBufferPoolTests.cs

@@ -0,0 +1,17 @@
+using NATS.Server.IO;
+
+namespace NATS.Server.Tests;
+
+public class OutboundBufferPoolTests
+{
+    [Theory]
+    [InlineData(100, 512)]
+    [InlineData(1000, 4096)]
+    [InlineData(10000, 64 * 1024)]
+    public void Rent_uses_three_tier_buffer_buckets(int requested, int expectedMinimum)
+    {
+        var pool = new OutboundBufferPool();
+        using var owner = pool.Rent(requested);
+        owner.Memory.Length.ShouldBeGreaterThanOrEqualTo(expectedMinimum);
+    }
+}