feat(deployment-manager): resolve DeploymentManager-006 — query site deployment state before redeploy and reconcile

Adds DeploymentStateQuery request/response contracts (Commons), a site-side
handler (SiteRuntime), a CommunicationService query method (Communication), and
reconciliation in DeploymentService: when a prior record is InProgress or
Failed-on-timeout, query the site; if it already holds the target revision hash
mark the record Success without re-sending; on query failure fall through to a
normal deploy (site-side stale-rejection is the safety net).

tests/ScadaLink.Communication.Tests/CommunicationServiceTests.cs

@@ -1,12 +1,15 @@
+using Akka.Actor;
+using Akka.TestKit.Xunit2;
 using Microsoft.Extensions.Logging.Abstractions;
 using Microsoft.Extensions.Options;
+using ScadaLink.Commons.Messages.Deployment;
 
 namespace ScadaLink.Communication.Tests;
 
 /// <summary>
 /// WP-2: Tests for CommunicationService initialization and state.
 /// </summary>
-public class CommunicationServiceTests
+public class CommunicationServiceTests : TestKit
 {
     [Fact]
     public async Task BeforeInitialization_ThrowsOnUsage()
@@ -18,7 +21,7 @@ public class CommunicationServiceTests
         // CommunicationService requires SetCommunicationActor before use
         await Assert.ThrowsAsync<InvalidOperationException>(() =>
             service.DeployInstanceAsync("site1",
-                new Commons.Messages.Deployment.DeployInstanceCommand(
+                new DeployInstanceCommand(
                     "dep1", "inst1", "hash1", "{}", "admin", DateTimeOffset.UtcNow)));
     }
 
@@ -30,4 +33,63 @@ public class CommunicationServiceTests
         Assert.NotNull(method);
         Assert.Equal(typeof(void), method!.ReturnType);
     }
+
+    // ── DeploymentManager-006: query-the-site-before-redeploy ──
+
+    [Fact]
+    public async Task QueryDeploymentStateAsync_BeforeInitialization_Throws()
+    {
+        var service = new CommunicationService(
+            Options.Create(new CommunicationOptions()),
+            NullLogger<CommunicationService>.Instance);
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            service.QueryDeploymentStateAsync("site1",
+                new DeploymentStateQueryRequest("corr-1", "inst1", DateTimeOffset.UtcNow)));
+    }
+
+    [Fact]
+    public async Task QueryDeploymentStateAsync_SendsEnvelopeAndReturnsResponse()
+    {
+        // The query must be dispatched as a SiteEnvelope over the existing
+        // command/control transport, exactly like other site-directed commands,
+        // and the typed response returned to the caller.
+        var service = new CommunicationService(
+            Options.Create(new CommunicationOptions()),
+            NullLogger<CommunicationService>.Instance);
+
+        // A probe stands in for CentralCommunicationActor: it asserts the
+        // envelope shape and replies with a typed response.
+        var commActor = Sys.ActorOf(Props.Create(() => new EchoStateQueryActor()));
+        service.SetCommunicationActor(commActor);
+
+        var request = new DeploymentStateQueryRequest("corr-9", "QueriedInst", DateTimeOffset.UtcNow);
+        var response = await service.QueryDeploymentStateAsync("site-a", request);
+
+        Assert.Equal("corr-9", response.CorrelationId);
+        Assert.Equal("QueriedInst", response.InstanceUniqueName);
+        Assert.True(response.IsDeployed);
+        Assert.Equal("sha256:applied", response.AppliedRevisionHash);
+    }
+
+    /// <summary>
+    /// Stand-in for CentralCommunicationActor: verifies the message is wrapped
+    /// in a SiteEnvelope targeting the requested site and replies with a typed
+    /// DeploymentStateQueryResponse.
+    /// </summary>
+    private class EchoStateQueryActor : ReceiveActor
+    {
+        public EchoStateQueryActor()
+        {
+            Receive<SiteEnvelope>(env =>
+            {
+                if (env is { SiteId: "site-a", Message: DeploymentStateQueryRequest req })
+                {
+                    Sender.Tell(new DeploymentStateQueryResponse(
+                        req.CorrelationId, req.InstanceUniqueName, true,
+                        "dep-applied", "sha256:applied", DateTimeOffset.UtcNow));
+                }
+            });
+        }
+    }
 }