feat: add CLI debug snapshot command for one-shot instance state inspection

Adds `debug snapshot --id <int>` to query a running instance's current
attribute values and alarm states without the subscribe/stream overhead
of the debug view. Routes through ManagementActor → CommunicationService
→ site DeploymentManager → InstanceActor using the existing remote query
pattern.

src/ScadaLink.Communication/Actors/SiteCommunicationActor.cs

@@ -104,6 +104,9 @@ public class SiteCommunicationActor : ReceiveActor, IWithTimers
         Receive<SubscribeDebugViewRequest>(msg => _deploymentManagerProxy.Forward(msg));
         Receive<UnsubscribeDebugViewRequest>(msg => _deploymentManagerProxy.Forward(msg));
 
+        // Pattern 6a: Debug Snapshot (one-shot) — forward to Deployment Manager
+        Receive<DebugSnapshotRequest>(msg => _deploymentManagerProxy.Forward(msg));
+
         // Pattern 7: Remote Queries
         Receive<EventLogQueryRequest>(msg =>
         {

src/ScadaLink.Communication/CommunicationService.cs

@@ -130,7 +130,17 @@ public class CommunicationService
         GetActor().Tell(new SiteEnvelope(siteId, request));
     }
 
-    // ── Pattern 6: Health Reporting (site→central, Tell) ──
+    // ── Pattern 6a: Debug Snapshot (one-shot, request/response) ──
+
+    public async Task<DebugViewSnapshot> RequestDebugSnapshotAsync(
+        string siteId, DebugSnapshotRequest request, CancellationToken cancellationToken = default)
+    {
+        var envelope = new SiteEnvelope(siteId, request);
+        return await GetActor().Ask<DebugViewSnapshot>(
+            envelope, _options.QueryTimeout, cancellationToken);
+    }
+
+    // ── Pattern 6b: Health Reporting (site→central, Tell) ──
     // Health reports are received by central, not sent. No method needed here.
 
     // ── Pattern 7: Remote Queries ──