feat(inbound): routed Route.To().WaitForAttribute — contract + central path (spec §6)

src/ZB.MOM.WW.ScadaBridge.InboundAPI/CommunicationServiceInstanceRouter.cs

@@ -35,4 +35,9 @@ public sealed class CommunicationServiceInstanceRouter : IInstanceRouter
     public Task<RouteToSetAttributesResponse> RouteToSetAttributesAsync(
         string siteId, RouteToSetAttributesRequest request, CancellationToken cancellationToken) =>
         _communicationService.RouteToSetAttributesAsync(siteId, request, cancellationToken);
+
+    /// <inheritdoc />
+    public Task<RouteToWaitForAttributeResponse> RouteToWaitForAttributeAsync(
+        string siteId, RouteToWaitForAttributeRequest request, CancellationToken cancellationToken) =>
+        _communicationService.RouteToWaitForAttributeAsync(siteId, request, cancellationToken);
 }

src/ZB.MOM.WW.ScadaBridge.InboundAPI/IInstanceRouter.cs

@@ -34,4 +34,12 @@ public interface IInstanceRouter
     /// <returns>A task that resolves to the set-attributes response from the target site.</returns>
     Task<RouteToSetAttributesResponse> RouteToSetAttributesAsync(
         string siteId, RouteToSetAttributesRequest request, CancellationToken cancellationToken);
+
+    /// <summary>Routes a wait-for-attribute request to the specified site (spec §6).</summary>
+    /// <param name="siteId">Target site identifier.</param>
+    /// <param name="request">The wait-for-attribute request to route (value-equality only).</param>
+    /// <param name="cancellationToken">Cancellation token for the routed call.</param>
+    /// <returns>A task that resolves to the wait-for-attribute response from the target site.</returns>
+    Task<RouteToWaitForAttributeResponse> RouteToWaitForAttributeAsync(
+        string siteId, RouteToWaitForAttributeRequest request, CancellationToken cancellationToken);
 }

src/ZB.MOM.WW.ScadaBridge.InboundAPI/RouteHelper.cs

@@ -205,6 +205,47 @@ public class RouteTarget
         return response.Values;
     }
 
+    /// <summary>
+    /// Blocks until a remote instance attribute reaches <paramref name="targetValue"/>
+    /// or <paramref name="timeout"/> elapses (spec §6). Value-equality ONLY across the
+    /// wire: the target is canonically encoded via <see cref="AttributeValueCodec"/> and
+    /// the site evaluates equality — there is no predicate and no quality flag in the
+    /// comparison.
+    /// </summary>
+    /// <param name="attributeName">Name of the attribute to wait on.</param>
+    /// <param name="targetValue">Target value the attribute must equal for the wait to match.</param>
+    /// <param name="timeout">Maximum time to wait for the attribute to reach the target value.</param>
+    /// <param name="cancellationToken">Optional cancellation token; defaults to the method deadline.</param>
+    /// <returns>A task that resolves to <c>true</c> if the attribute reached the target value, <c>false</c> if the wait timed out.</returns>
+    public async Task<bool> WaitForAttribute(
+        string attributeName,
+        object? targetValue,
+        TimeSpan timeout,
+        CancellationToken cancellationToken = default)
+    {
+        var token = Effective(cancellationToken);
+        var siteId = await ResolveSiteAsync(token);
+
+        // Audit Log #23 (ParentExecutionId): mirrors the Call path — stamp the
+        // spawning inbound request's ExecutionId so future site-side audit
+        // emission for routed waits can record this wait's parent. CorrelationId
+        // is the per-operation lifecycle id, freshly minted per routed wait.
+        var request = new RouteToWaitForAttributeRequest(
+            Guid.NewGuid().ToString(), _instanceCode, attributeName,
+            AttributeValueCodec.Encode(targetValue), timeout, DateTimeOffset.UtcNow,
+            _parentExecutionId);
+
+        var response = await _instanceRouter.RouteToWaitForAttributeAsync(siteId, request, token);
+
+        if (!response.Success)
+        {
+            throw new InvalidOperationException(
+                response.ErrorMessage ?? "Remote attribute wait failed");
+        }
+
+        return response.Matched;
+    }
+
     /// <summary>
     /// Sets a single attribute value on the remote instance.
     /// </summary>