feat: consolidate legacy parity migration baseline

src/MBN_STOCK_WEBVIEW.LegacyParityApp/MainWindow.Playout.cs

@@ -178,8 +178,9 @@ public sealed partial class MainWindow
             {
                 case LegacyOperatorPlayoutCommand.Prepare:
                     var request = gateAPrepareRequest ??
-                        _controller.CreatePlayoutRequest(
-                            _compositionOptions!.Current.FadeDuration);
+                        await CreateFreshPagedPlayoutRequestAsync(
+                            workflow,
+                            cancellationToken).ConfigureAwait(false);
                     result = await workflow.PrepareAsync(
                         request.Playlist,
                         request.SelectedIndexZeroBased,
@@ -190,8 +191,9 @@ public sealed partial class MainWindow
                     // candidate) to m_crow and ran ONAirMode + Play, even while another
                     // row was already on air. Re-read the current selection on every F8;
                     // a stale explicit PREPARE must never override a later row click.
-                    var takeInRequest = _controller.CreatePlayoutRequest(
-                        _compositionOptions!.Current.FadeDuration);
+                    var takeInRequest = await CreateFreshPagedPlayoutRequestAsync(
+                        workflow,
+                        cancellationToken).ConfigureAwait(false);
                     result = await workflow.TakeSelectedAsync(
                         takeInRequest.Playlist,
                         takeInRequest.SelectedIndexZeroBased,
@@ -280,6 +282,61 @@ public sealed partial class MainWindow
         }
     }
 
+    private async Task<LegacyOperatorPlayoutRequest> CreateFreshPagedPlayoutRequestAsync(
+        LegacyPlayoutWorkflow workflow,
+        CancellationToken cancellationToken)
+    {
+        var fadeDuration = _compositionOptions!.Current.FadeDuration;
+        var request = _controller.CreatePlayoutRequest(fadeDuration);
+
+        // The first PREPARE/TAKE IN freezes the complete playlist. Resolve every
+        // operator PageN row from a fresh read-only DB preflight before that snapshot
+        // is handed to the workflow. A later F8 while PREPARED/PROGRAM reuses the
+        // already-frozen 1/N values and must not query a second navigation contract.
+        if (workflow.State.CurrentEntryId is not null)
+        {
+            return request;
+        }
+
+        var pagedEntries = request.Playlist
+            .Where(static entry => entry.PageNavigation?.PageSize.HasValue == true)
+            .ToArray();
+        if (pagedEntries.Length == 0)
+        {
+            return request;
+        }
+
+        var plans = await workflow.PreflightPagePlansAsync(
+            Array.AsReadOnly(pagedEntries),
+            cancellationToken).ConfigureAwait(false);
+        if (plans.Count != pagedEntries.Length)
+        {
+            throw new LegacySceneDataException(
+                "The playlist page preflight did not return every PageN entry.");
+        }
+
+        foreach (var plan in plans)
+        {
+            var entry = pagedEntries.SingleOrDefault(candidate =>
+                string.Equals(candidate.EntryId, plan.EntryId, StringComparison.Ordinal));
+            if (entry?.PageNavigation?.PageSize is not { } expectedPageSize ||
+                plan.PageSize != (int)expectedPageSize ||
+                plan.PageCount is < 1 or > ScenePaging.MaximumPageCount)
+            {
+                throw new LegacySceneDataException(
+                    "The playlist page preflight does not match the operator PageN row.");
+            }
+
+            _controller.ReflectSuccessfulPlayout(
+                plan.EntryId,
+                pageIndexZeroBased: 0,
+                pageCount: plan.PageCount,
+                synchronizeOperatorSelection: false);
+        }
+
+        return _controller.CreatePlayoutRequest(fadeDuration);
+    }
+
     private async Task<LegacyOperatorSnapshot> ExecuteGateAPrepareAsync(
         string capability,
         CancellationToken cancellationToken)
@@ -596,9 +653,7 @@ public sealed partial class MainWindow
     }
 
     private static bool IsOperatorMutationIntent(LegacyUiIntent intent) => intent is
-        LegacyCutPointerDownIntent or
-        LegacyCutKeyDownIntent or
-        LegacyClearCutSelectionIntent or
+        LegacyCutPointerDownIntent { AllowAppend: true } or
         LegacyDropSelectedCutsIntent or
         LegacySetPlaylistEnabledIntent or
         LegacySetAllPlaylistEnabledIntent or
@@ -948,6 +1003,7 @@ public sealed partial class MainWindow
                 }
 
                 var intentGateEntered = false;
+                var databaseGateEntered = false;
                 var playoutGateEntered = false;
                 try
                 {
@@ -958,6 +1014,9 @@ public sealed partial class MainWindow
                     _intentBusy = true;
                     QueueOperatorState();
 
+                    await AcquirePriorityDatabaseActivityAsync(token).ConfigureAwait(false);
+                    databaseGateEntered = true;
+
                     await _playoutCommandGate.WaitAsync(token).ConfigureAwait(false);
                     playoutGateEntered = true;
                     Interlocked.Exchange(ref _playoutBusy, 1);
@@ -1058,6 +1117,11 @@ public sealed partial class MainWindow
                         _playoutCommandGate.Release();
                     }
 
+                    if (databaseGateEntered)
+                    {
+                        _databaseActivityGate.Release();
+                    }
+
                     if (intentGateEntered)
                     {
                         _intentBusy = false;