TASK 51 slice 3: per-scene webcam BackgroundEffect + BackgroundStrength on WebcamSceneConfig, persisted via additive guarded columns; radio-pill bools RemoveBackground/BlurBackground (Unit: bg-effect config)

ytLive.Tests/LayoutStorePersistenceTests.cs

@@ -128,6 +128,57 @@ public class LayoutStorePersistenceTests
         }
     }
 
+    /// <summary>TASK 51 slice 3: each scene's webcam background effect + strength survives a
+    /// save and a reopen; a pre-TASK-51 DB (no columns) migrates in place and reads None/0.5.</summary>
+    [Fact]
+    public void Webcam_Background_Effect_Round_Trips_Per_Scene_And_Legacy_Db_Migrates()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"ytLlive-layout-{Guid.NewGuid():N}.db");
+        try
+        {
+            var webcam = new Webcam { DeviceId = "real-device", Name = "Logitech" };
+            var live = new Scene { Name = "Live" };
+            live.Elements.Add(new WebcamSceneConfig { WebcamId = webcam.Id, Width = 480, Height = 270, BackgroundEffect = BackgroundEffect.Remove, BackgroundStrength = 0.2 });
+            var chat = new Scene { Name = "Chat" };
+            chat.Elements.Add(new WebcamSceneConfig { WebcamId = webcam.Id, Width = 480, Height = 270, BackgroundEffect = BackgroundEffect.Blur, BackgroundStrength = 0.8 });
+            using (var store = new LayoutStore(path))
+                store.Save(new[] { live, chat }, webcam, null);
+
+            using (var reopened = new LayoutStore(path))
+            {
+                var scenes = reopened.Load();
+                var liveCfg = scenes.Single(s => s.Name == "Live").Elements.OfType<WebcamSceneConfig>().Single();
+                var chatCfg = scenes.Single(s => s.Name == "Chat").Elements.OfType<WebcamSceneConfig>().Single();
+                Assert.Equal(BackgroundEffect.Remove, liveCfg.BackgroundEffect);
+                Assert.Equal(0.2, liveCfg.BackgroundStrength, 6);
+                Assert.Equal(BackgroundEffect.Blur, chatCfg.BackgroundEffect);
+                Assert.Equal(0.8, chatCfg.BackgroundStrength, 6);
+            }
+
+            // Simulate a DB written before TASK 51: drop the two columns, reopen.
+            SqliteConnection.ClearAllPools();
+            using (var raw = new SqliteConnection($"Data Source={path}"))
+            {
+                raw.Open();
+                using var cmd = raw.CreateCommand();
+                cmd.CommandText = "ALTER TABLE WebcamSceneConfig DROP COLUMN BackgroundEffect; ALTER TABLE WebcamSceneConfig DROP COLUMN BackgroundStrength;";
+                cmd.ExecuteNonQuery();
+            }
+            SqliteConnection.ClearAllPools();
+            using (var legacy = new LayoutStore(path))
+            {
+                var cfg = legacy.Load().SelectMany(s => s.Elements).OfType<WebcamSceneConfig>().First();
+                Assert.Equal(BackgroundEffect.None, cfg.BackgroundEffect);
+                Assert.Equal(0.5, cfg.BackgroundStrength, 6);
+            }
+        }
+        finally
+        {
+            SqliteConnection.ClearAllPools();
+            try { File.Delete(path); } catch { /* best-effort cleanup */ }
+        }
+    }
+
     // The background (schema v5): permanent bottom layer holding live desktop/game
     // capture. IsBackground + CaptureKey must survive a save + reload so a
     // re-designated target isn't lost on restart.