test: add E2E leaf node tests (hub-to-leaf, leaf-to-hub, subject propagation)

Fix LeafNodeManager.StartAsync to launch solicited connections for RemoteLeaves
(config-file-parsed remotes) in addition to the programmatic Remotes list, and
update ParseEndpoint to handle nats-leaf:// scheme URLs. Add LeafNodeFixture
that polls /leafz for connection readiness and three E2E tests covering
hub→leaf delivery, leaf→hub delivery, and subject-scoped propagation.

src/NATS.Server/LeafNodes/LeafNodeManager.cs

@@ -239,6 +239,16 @@ public sealed class LeafNodeManager : IAsyncDisposable
         foreach (var remote in _options.Remotes.Distinct(StringComparer.OrdinalIgnoreCase))
             _ = Task.Run(() => ConnectSolicitedWithRetryAsync(remote, _options.JetStreamDomain, _cts.Token));
 
+        // Also start solicited connections for remotes parsed from the config file (RemoteLeaves).
+        // RemoteLeaves are populated by the config parser from leafnodes.remotes[] blocks;
+        // _options.Remotes is the simple programmatic list only.
+        // Go reference: leafnode.go — createLeafNode starts solicited connections via connectToRemoteLeaf.
+        foreach (var remoteLeaf in _options.RemoteLeaves)
+        {
+            foreach (var url in remoteLeaf.Urls.Distinct(StringComparer.OrdinalIgnoreCase))
+                _ = Task.Run(() => ConnectSolicitedWithRetryAsync(url, _options.JetStreamDomain, _cts.Token));
+        }
+
         _logger.LogDebug("Leaf manager started (listen={Host}:{Port})", _options.Host, _options.Port);
         return Task.CompletedTask;
     }
@@ -819,6 +829,12 @@ public sealed class LeafNodeManager : IAsyncDisposable
 
     private static IPEndPoint ParseEndpoint(string endpoint)
     {
+        // Handle full URLs with a scheme (e.g. "nats-leaf://127.0.0.1:5222").
+        // Uri.TryCreate handles both schemed URLs and bare "host:port" strings.
+        if (Uri.TryCreate(endpoint, UriKind.Absolute, out var uri))
+            return new IPEndPoint(IPAddress.Parse(uri.Host), uri.Port);
+
+        // Fall back to bare "host:port" splitting for plain strings without a scheme.
         var parts = endpoint.Split(':', 2, StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
         if (parts.Length != 2)
             throw new FormatException($"Invalid endpoint: {endpoint}");

tests/NATS.E2E.Tests/Infrastructure/LeafNodeFixture.cs

@@ -0,0 +1,92 @@
+using System.Net.Http.Json;
+using NATS.Client.Core;
+
+namespace NATS.E2E.Tests.Infrastructure;
+
+public sealed class LeafNodeFixture : IAsyncLifetime
+{
+    private NatsServerProcess _hub = null!;
+    private NatsServerProcess _leaf = null!;
+
+    public int HubPort => _hub.Port;
+    public int LeafPort => _leaf.Port;
+
+    public async Task InitializeAsync()
+    {
+        var leafListenPort = NatsServerProcess.AllocateFreePort();
+
+        var hubConfig = $$"""
+            server_name: hub
+            leafnodes {
+                listen: 127.0.0.1:{{leafListenPort}}
+            }
+            """;
+
+        _hub = NatsServerProcess.WithConfig(hubConfig, enableMonitoring: true);
+        await _hub.StartAsync();
+
+        var leafConfig = $$"""
+            server_name: leaf
+            leafnodes {
+                remotes [
+                    { url: "nats-leaf://127.0.0.1:{{leafListenPort}}" }
+                ]
+            }
+            """;
+
+        _leaf = NatsServerProcess.WithConfig(leafConfig);
+        await _leaf.StartAsync();
+
+        // Poll hub's /leafz until it reports 1 connected leaf node
+        await WaitForLeafConnectionAsync();
+    }
+
+    private async Task WaitForLeafConnectionAsync()
+    {
+        using var http = new HttpClient { Timeout = TimeSpan.FromSeconds(2) };
+        using var deadline = new CancellationTokenSource(TimeSpan.FromSeconds(30));
+        using var timer = new PeriodicTimer(TimeSpan.FromMilliseconds(200));
+
+        while (await timer.WaitForNextTickAsync(deadline.Token).ConfigureAwait(false))
+        {
+            try
+            {
+                var leafz = await http.GetFromJsonAsync<Leafz>(
+                    $"http://127.0.0.1:{_hub.MonitorPort!.Value}/leafz",
+                    deadline.Token);
+
+                if (leafz?.NumLeafs >= 1)
+                    return;
+            }
+            catch (Exception ex) when (ex is HttpRequestException or TaskCanceledException
+                                        && !deadline.IsCancellationRequested)
+            {
+                // Monitor not yet ready or per-request timeout — retry on next tick
+                _ = ex;
+            }
+        }
+
+        throw new TimeoutException("Leaf node did not connect to hub within 30s.");
+    }
+
+    public async Task DisposeAsync()
+    {
+        await _leaf.DisposeAsync();
+        await _hub.DisposeAsync();
+    }
+
+    public NatsConnection CreateHubClient()
+        => new(new NatsOpts { Url = $"nats://127.0.0.1:{HubPort}" });
+
+    public NatsConnection CreateLeafClient()
+        => new(new NatsOpts { Url = $"nats://127.0.0.1:{LeafPort}" });
+
+    private sealed class Leafz
+    {
+        [System.Text.Json.Serialization.JsonPropertyName("num_leafs")]
+        public int NumLeafs { get; init; }
+    }
+}
+
+[CollectionDefinition("E2E-LeafNode")]
+public class LeafNodeCollection : ICollectionFixture<LeafNodeFixture>;