feat(quic): replace probe UDP data plane with QUIC datagrams

backend/tests/MoShiro.Backend.Analysis.Tests/OpTests.cs

@@ -90,6 +90,28 @@ public sealed class OpTests
         Assert.Equal(2, ((RunLengthAcc)EvaluateOneBucket(chunk, "loss.run").Items["loss.run"]).Max);
     }
 
+    [Fact]
+    public void LossRuns_AreSeparatedByDirection_AndDownstreamExcludesRequestsLostUpstream()
+    {
+        bool[] upLost = [false, true, true, false, false, false, true, true];
+        bool[] downLost = [false, false, true, true, false, true, false, true];
+        RawChunk chunk = ChunkFactory.Echo(s_agent, "udp_echo", T0, upLost.Length, 100,
+            i => new EchoPacket(upLost[i], downLost[i], 20_000, 20_000));
+
+        MetricSet set = EvaluateOneBucket(chunk, "loss.run.up", "loss.run.down");
+        Assert.Equal(2, ((MaxAcc)set.Items["loss.run.up"]).Result);
+        Assert.Equal(1, ((MaxAcc)set.Items["loss.run.down"]).Result);
+    }
+
+    [Fact]
+    public void LossRuns_NoLoss_ExportsZeroForBothDirections()
+    {
+        RawChunk chunk = ChunkFactory.UdpEchoClean(s_agent, T0, count: 8);
+        MetricSet set = EvaluateOneBucket(chunk, "loss.run.up", "loss.run.down");
+        Assert.Equal(0, ((MaxAcc)set.Items["loss.run.up"]).Result);
+        Assert.Equal(0, ((MaxAcc)set.Items["loss.run.down"]).Result);
+    }
+
     [Fact]
     public void Reorder_CountsLateArrivals_AndIgnoresDuplicates()
     {