feat(lmxproxy): active health probing + address-based subscription cleanup (gap 1 & 2)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lmxproxy/src/ZB.MOM.WW.LmxProxy.Host/Domain/IScadaClient.cs

@@ -57,6 +57,18 @@ namespace ZB.MOM.WW.LmxProxy.Host.Domain
             int pollIntervalMs,
             CancellationToken ct = default);
 
+        /// <summary>
+        ///     Probes connection health by reading a test tag.
+        ///     Returns a classified result: Healthy, TransportFailure, or DataDegraded.
+        /// </summary>
+        Task<ProbeResult> ProbeConnectionAsync(string testTagAddress, int timeoutMs, CancellationToken ct = default);
+
+        /// <summary>
+        ///     Unsubscribes specific tag addresses. Removes from stored subscriptions
+        ///     and COM state. Safe to call after reconnect -- uses current handle mappings.
+        /// </summary>
+        Task UnsubscribeByAddressAsync(IEnumerable<string> addresses);
+
         /// <summary>Subscribes to value changes for specified addresses.</summary>
         /// <returns>Subscription handle for unsubscribing.</returns>
         Task<IAsyncDisposable> SubscribeAsync(