feat: complete final jetstream parity transport and runtime baselines

tests/NATS.Server.Tests/RoutePoolTests.cs

@@ -0,0 +1,11 @@
+namespace NATS.Server.Tests;
+
+public class RoutePoolTests
+{
+    [Fact]
+    public async Task Route_manager_establishes_default_pool_of_three_links_per_peer()
+    {
+        await using var fx = await RouteFixture.StartTwoNodeClusterAsync();
+        (await fx.ServerARouteLinkCountToServerBAsync()).ShouldBe(3);
+    }
+}