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

backend/agent/src/MoShiro.Agent/DataPlane/Registries.cs

@@ -44,7 +44,7 @@ public sealed class ProbeSession : DataSession
 {
     private readonly ConcurrentDictionary<uint, ReplayWindow> _windows = new();
     private readonly ConcurrentDictionary<ulong, byte> _nonces = new();
-    private SocketAddress? _udpSource;
+    private SocketAddress? _datagramSource;
 
     public ProbeSession(PeerSessionInfo info)
         : base(info.Credentials.SessionIdValue, info.Credentials.Key)
@@ -71,11 +71,11 @@ public sealed class ProbeSession : DataSession
     public RpcSession<PeerContext>? Rpc { get; set; }
 
     /// <summary>最近一次认证通过的 UDP 包的源地址（Agent 把单向数据发往这里）。</summary>
-    public override IPEndPoint? UdpEndpoint
+    public override IPEndPoint? DatagramRemoteEndPoint
     {
         get
         {
-            SocketAddress? source = Volatile.Read(ref _udpSource);
+            SocketAddress? source = Volatile.Read(ref _datagramSource);
             return source is null ? null : (IPEndPoint)new IPEndPoint(source.Family == AddressFamily.InterNetworkV6 ? IPAddress.IPv6Any : IPAddress.Any, 0).Create(source);
         }
     }
@@ -83,7 +83,7 @@ public sealed class ProbeSession : DataSession
     /// <summary>记录 UDP 源地址；NAT 映射变化后地址变了返回 true（上报 endpoint_changed）。第一次看到地址不算变化。</summary>
     public bool UpdateSource(SocketAddress source)
     {
-        SocketAddress? previous = Volatile.Read(ref _udpSource);
+        SocketAddress? previous = Volatile.Read(ref _datagramSource);
         if (previous is not null && previous.Equals(source))
         {
             return false;
@@ -96,7 +96,7 @@ public sealed class ProbeSession : DataSession
             copy[i] = source[i];
         }
 
-        Volatile.Write(ref _udpSource, copy);
+        Volatile.Write(ref _datagramSource, copy);
         return previous is not null;
     }
 
@@ -312,7 +312,7 @@ public sealed class AgentAdmission : IAdmission
     /// <summary>NAT 映射变化，源地址变了：上报 <c>endpoint_changed</c>。</summary>
     public Action<ProbeSession>? OnEndpointChanged { get; set; }
 
-    public Admission AdmitPacket(DataSession session, in UdpHeader header, SocketAddress source, long nowUs)
+    public Admission AdmitDatagram(DataSession session, in MeasurementDatagramHeader header, SocketAddress source, long nowUs)
     {
         if (session is not ProbeSession probe || !_streams.TryGet(header.StreamId, out StreamInfo? stream) || !ReferenceEquals(stream.Owner, probe) || !probe.AcceptSequence(header.StreamId, header.Seq))
         {