feat!: pre-handshake knock on the agent TCP ports; probes get the agent certificate public key [CI]

backend/agent/src/MoShiro.Agent/Tasks/TaskManager.cs

@@ -52,6 +52,9 @@ public sealed class TaskManager
     /// <summary>点对点握手时查找 Probe 的公钥（SPKI）。</summary>
     public byte[]? LookupPeerKey(string peerId) => _peers.TryGetValue(peerId, out byte[]? key) ? key : null;
 
+    /// <summary>名册里全部 Probe 的公钥：敲门关卡用它们派生配对密钥。</summary>
+    public IReadOnlyList<byte[]> PeerKeys() => [.. _peers.Values];
+
     /// <summary>一个新的 Probe 会话开始：为它登记全部线路任务的流并启动监听方积木，返回要下发给它的线路任务集。</summary>
     public LineTaskSet OpenSession(ProbeSession probe)
     {