agent: unify listening and dialing with directed mutual measurements

Replace Probe with Agent across node runtime, Fleet contracts, backend state, API and storage. Report incoming sessions and outgoing link health through each Agent uplink, and retain directed link controls and retry.

Update protocol fixtures and end-to-end coverage for the unified model; accept requested cancellation during the Fleet timeout test cleanup.

backend/agent/src/MoShiro.Agent/AgentConfig.cs

@@ -44,23 +44,20 @@ public sealed class FleetSection
 
 public sealed class ListenSection
 {
+    /// <summary>是否接受拨号方的连接。关闭时节点只拨出：不开任何端口，在 Backend 的目录里也不是拨号目标（家宽和 NAT 后的节点用这个配置）。</summary>
+    [JsonPropertyName("enabled")]
+    public bool Enabled { get; set; } = true;
+
     [JsonPropertyName("bind")]
     public string Bind { get; set; } = "::";
 
-    /// <summary>Probe 控制通道（TLS，点对点会话）。</summary>
+    /// <summary>拨号方 控制通道（TLS，点对点会话）。</summary>
     [JsonPropertyName("control_port")]
     public int ControlPort { get; set; } = 7443;
 
     [JsonPropertyName("quic_ports")]
     public List<int> QuicPorts { get; set; } = [7443];
 
-    /// <summary>Legacy config key accepted while deployments migrate to QUIC Datagram.</summary>
-    [JsonPropertyName("udp_ports")]
-    public List<int>? LegacyUdpPorts { get; set; }
-
-    [JsonIgnore]
-    public IReadOnlyList<int> EffectiveQuicPorts => LegacyUdpPorts ?? QuicPorts;
-
     [JsonPropertyName("tcp_ports")]
     public List<int> TcpPorts { get; set; } = [7444];
 }
@@ -89,4 +86,6 @@ public sealed class PolicySection
 }
 
 [JsonSerializable(typeof(AgentConfig))]
+[JsonSerializable(typeof(DialCache))]
+[JsonSerializable(typeof(OpenWrtHealth))]
 public sealed partial class AgentConfigContext : System.Text.Json.Serialization.JsonSerializerContext;