chore(management): log debug-stream push failures; fix event-log filter docs; refresh stale SourceNode note (arch-review S5/C7/C8)

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.ManagementService/DebugStreamHub.cs

@@ -198,13 +198,15 @@ public class DebugStreamHub : Hub
             // Use IHubContext for callbacks — the hub instance is transient (disposed after method returns),
             // but IHubContext is a singleton that remains valid for the lifetime of the connection.
             var hubClients = _hubContext.Clients;
+            // Capture the logger into a local: the callbacks outlive this (transient)
+            // hub instance, and ILogger is a singleton, so this is safe to hold.
+            var logger = _logger;
 
             var session = await _debugStreamService.StartStreamAsync(
                 instanceId,
                 onEvent: evt =>
                 {
-                    // Fire-and-forget — if the client disconnects, SendAsync will fail silently
-                    _ = evt switch
+                    var send = evt switch
                     {
                         AttributeValueChanged changed =>
                             hubClients.Client(connectionId).SendAsync("OnAttributeChanged", changed),
@@ -214,10 +216,20 @@ public class DebugStreamHub : Hub
                             hubClients.Client(connectionId).SendAsync("OnSnapshot", snapshot),
                         _ => Task.CompletedTask
                     };
+                    // Fire-and-forget (deliberate — a slow/dead client must not block the
+                    // stream), but log the push failure rather than swallowing it silently.
+                    _ = send.ContinueWith(
+                        t => logger.LogWarning(t.Exception?.GetBaseException(),
+                            "Debug stream push to connection {ConnectionId} failed", connectionId),
+                        CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, TaskScheduler.Default);
                 },
                 onTerminated: () =>
                 {
-                    _ = hubClients.Client(connectionId).SendAsync("OnStreamTerminated", "Site disconnected");
+                    _ = hubClients.Client(connectionId).SendAsync("OnStreamTerminated", "Site disconnected")
+                        .ContinueWith(
+                            t => logger.LogWarning(t.Exception?.GetBaseException(),
+                                "Debug stream termination push to connection {ConnectionId} failed", connectionId),
+                            CancellationToken.None, TaskContinuationOptions.OnlyOnFaulted, TaskScheduler.Default);
                 });
 
             Context.Items[SessionIdKey] = session.SessionId;