fix: prevent QUIC heartbeat stalls and isolate TCP retransmission counters [CI] [SKIP TESTS]

backend/probe/src/MoShiro.Probe/ProbeApp.cs

@@ -171,10 +171,13 @@ public sealed class ProbeApp : IDisposable
 
     private List<ProbeQuicLinkHealth> SnapshotQuicLinks()
     {
+        AgentConnection[] connections;
         lock (_connections)
         {
-            return [.. _connections.Values.Select(r => r.Connection.QuicHealth())];
+            connections = [.. _connections.Values.Select(r => r.Connection)];
         }
+
+        return [.. connections.Select(c => c.QuicHealth())];
     }
 
     public async Task RunAsync(CancellationToken ct)