fix: settle canceled market data requests

MainWindow.xaml.cs

@@ -287,6 +287,7 @@ public sealed partial class MainWindow : Window
 
             await _databaseActivityGate.WaitAsync(requestCancellation.Token);
             databaseActivityEntered = true;
+            requestCancellation.Token.ThrowIfCancellationRequested();
 
             // Close the race where playout starts after this request is published
             // but before its market query begins.
@@ -317,7 +318,26 @@ public sealed partial class MainWindow : Window
         }
         catch (OperationCanceledException) when (requestCancellation.IsCancellationRequested)
         {
-            // A newer navigation request or app shutdown superseded this response.
+            PostPlayoutPriorityMarketDataCancellationIfCurrent(
+                requestId,
+                view,
+                requestCancellation);
+        }
+        catch (DatabaseOperationException) when (requestCancellation.IsCancellationRequested)
+        {
+            // Some providers surface a provider exception instead of cancellation after
+            // a command has already taken priority. Never publish that stale failure.
+            PostPlayoutPriorityMarketDataCancellationIfCurrent(
+                requestId,
+                view,
+                requestCancellation);
+        }
+        catch (Exception) when (requestCancellation.IsCancellationRequested)
+        {
+            PostPlayoutPriorityMarketDataCancellationIfCurrent(
+                requestId,
+                view,
+                requestCancellation);
         }
         catch (DatabaseOperationException exception)
         {
@@ -346,6 +366,26 @@ public sealed partial class MainWindow : Window
         }
     }
 
+    private void PostPlayoutPriorityMarketDataCancellationIfCurrent(
+        string requestId,
+        MarketDataView view,
+        CancellationTokenSource requestCancellation)
+    {
+        if (_lifetimeCancellation.IsCancellationRequested ||
+            !ReferenceEquals(
+                Volatile.Read(ref _marketDataCancellation),
+                requestCancellation))
+        {
+            // App shutdown or a newer navigation request superseded this response.
+            return;
+        }
+
+        PostMarketDataError(
+            requestId,
+            view,
+            "송출 명령과 자동 갱신을 우선 처리하기 위해 조회를 취소했습니다. 다시 조회하세요.");
+    }
+
     private void PostMarketDataError(string requestId, MarketDataView view, string message)
     {
         PostMessage("market-data-error", new