shared: add independent IPv4 and IPv6 collection [CI]

backend/probe/tests/MoShiro.Probe.Tests/ProbeTests.cs

@@ -6,6 +6,31 @@ namespace MoShiro.Probe.Tests;
 
 public sealed class ProbeTests
 {
+    [Fact]
+    public void AgentDirectory_DualStack_PersistsBothPaths_AndRemovingIpv6KeepsIpv4()
+    {
+        string directory = NewDirectory();
+        try
+        {
+            var agents = new AgentDirectory(new ConfigStore(directory), directory, NullNodeLog.Instance);
+            ProbeAgentList list = List(1, "agt_dual");
+            list.Agents[0].Ipv6Host = "2001:db8::1";
+            agents.Apply(list);
+            Assert.Equal(new[] { "ipv4", "ipv6" }, agents.Agents.Select(a => a.IpVersion));
+            var reloaded = new AgentDirectory(new ConfigStore(directory), directory, NullNodeLog.Instance);
+            Assert.Equal(2, reloaded.Agents.Count);
+            Assert.Equal("2001:db8::1", reloaded.Agents[1].Host);
+            list.Version = 2;
+            list.Agents[0].Ipv6Host = null;
+            reloaded.Apply(list);
+            Assert.Equal("ipv4", Assert.Single(reloaded.Agents).IpVersion);
+        }
+        finally
+        {
+            Directory.Delete(directory, recursive: true);
+        }
+    }
+
     [Fact]
     public void ClockEstimator_UsesTheSampleWithTheShortestRoundTrip()
     {