Web source: fix rendering — fixed 1920×1080 viewport (OBS pattern), Stretch=Uniform, startup registration

Services/WebView2Manager.cs

@@ -40,10 +40,13 @@ public sealed class WebView2Manager : IDisposable
     {
         if (_sessions.ContainsKey(source.Id)) return;
 
+        // OBS pattern: the browser viewport is the canvas size (1920×1080),
+        // never the element box. The page renders full at its designed size;
+        // the preview scales the captured frame independently (Stretch=Uniform).
         var webView = new WebView2
         {
-            Width = source.Width > 0 ? source.Width : 640,
-            Height = source.Height > 0 ? source.Height : 480,
+            Width = 1920,
+            Height = 1080,
             DefaultBackgroundColor = System.Drawing.Color.Transparent,
             Visibility = System.Windows.Visibility.Visible,
         };
@@ -65,21 +68,6 @@ public sealed class WebView2Manager : IDisposable
 
         _sessions[source.Id] = session;
 
-        source.PropertyChanged += (_, e) =>
-        {
-            if (e.PropertyName == nameof(Source.Width) || e.PropertyName == nameof(Source.Height))
-            {
-                var w = Math.Max(1, (int)source.Width);
-                var h = Math.Max(1, (int)source.Height);
-                if (Math.Abs(session.Control.Width - w) > 0.5 ||
-                    Math.Abs(session.Control.Height - h) > 0.5)
-                {
-                    session.Control.Width = w;
-                    session.Control.Height = h;
-                }
-            }
-        };
-
         timer.Tick += (_, _) =>
         {
             if (!session.Disposed && session.Initialized)
@@ -132,6 +120,7 @@ public sealed class WebView2Manager : IDisposable
                 _ = cws.ExecuteScriptAsync(
                     "document.documentElement.style.background='transparent';" +
                     "document.body.style.background='transparent';");
+                _ = CaptureFrame(source.Id);
             };
 
             session.Initialized = true;