TASK 3 milestone 1: webcam capture (MediaCapture CPU-first, CameraManager refcount, picker, clip/mirror, schema v2, tests)

Models/Source.cs

@@ -1,6 +1,7 @@
 using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Windows.Media;
+using System.Windows.Media.Imaging;
 using ytLive.Helpers;
 
 namespace ytLive.Models;
@@ -15,6 +16,12 @@ public enum SourceType
     TextOverlay
 }
 
+public enum ClipShape
+{
+    Traditional,
+    Round
+}
+
 public class Source : INotifyPropertyChanged
 {
     public event PropertyChangedEventHandler? PropertyChanged;
@@ -52,6 +59,54 @@ public class Source : INotifyPropertyChanged
     private string? _deviceId;
     public string? DeviceId { get => _deviceId; set => Set(ref _deviceId, value); }
 
+    // Webcam live preview: the shared WriteableBitmap owned by CameraManager.
+    private WriteableBitmap? _videoImageSource;
+    public WriteableBitmap? VideoImageSource
+    {
+        get => _videoImageSource;
+        set
+        {
+            if (Set(ref _videoImageSource, value))
+                Raise(nameof(DisplaySource));
+        }
+    }
+
+    private ClipShape _clipShape = ClipShape.Traditional;
+    public ClipShape ClipShape
+    {
+        get => _clipShape;
+        set
+        {
+            if (Set(ref _clipShape, value))
+                Raise(nameof(ShapeButtonText));
+        }
+    }
+
+    private bool _isMirrored;
+    public bool IsMirrored
+    {
+        get => _isMirrored;
+        set
+        {
+            if (Set(ref _isMirrored, value))
+            {
+                Raise(nameof(MirrorScale));
+                Raise(nameof(MirrorButtonText));
+            }
+        }
+    }
+
+    public double MirrorScale => IsMirrored ? -1 : 1;
+
+    /// <summary>Mirror toggle label (mirrored → "Unmirror").</summary>
+    public string MirrorButtonText => IsMirrored ? "Unmirror" : "Mirror";
+
+    /// <summary>Clip-shape toggle label (round → "Rect").</summary>
+    public string ShapeButtonText => ClipShape == ClipShape.Round ? "Rect" : "Round";
+
+    /// <summary>What the preview shows: static image for image/background, live frames for webcam.</summary>
+    public ImageSource? DisplaySource => Type == SourceType.Webcam ? _videoImageSource : _imageSource;
+
     // Image (asset stored in the layout database)
     private string? _assetId;
     private ImageSource? _imageSource;
@@ -65,6 +120,7 @@ public class Source : INotifyPropertyChanged
             {
                 _imageSource = ImageCache.Get(value ?? string.Empty);
                 Raise(nameof(ImageSource));
+                Raise(nameof(DisplaySource));
             }
         }
     }