feat(37): restore all scenes to factory defaults

Services/LayoutStore.Snapshots.cs

@@ -165,6 +165,16 @@ public partial class LayoutStore : IDisposable
         return true;
     }
 
+    /// <summary>Restores the full factory snapshot without changing the active build stamp.</summary>
+    public bool RestoreAllDefaults()
+    {
+        if (GetSnapshotState(DefaultsInitializedKey) != "1") return false;
+        var buildId = GetSnapshotState(CurrentBuildIdKey);
+        if (string.IsNullOrWhiteSpace(buildId)) return false;
+        RestoreDefaults(buildId);
+        return true;
+    }
+
     private string? GetCurrentWebcamId()
     {
         using var cmd = _connection.CreateCommand();

ytLive.Tests/LayoutStoreSnapshotTests.cs

@@ -149,6 +149,42 @@ public sealed class LayoutStoreSnapshotTests
         }
     }
 
+    [Fact]
+    public void ResetAllScenes_RestoresTheFactorySnapshot()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"ytLlive-layout-snapshot-{Guid.NewGuid():N}.db");
+        var starting = MakeScene(SceneCatalog.Starting, "Factory starting");
+        var brb = MakeScene(SceneCatalog.Brb, "Factory BRB");
+        try
+        {
+            using (var store = new LayoutStore(path))
+            {
+                store.Save(new[] { starting, brb }, null, null);
+                store.PrepareLayoutSnapshots("build-a");
+                store.Save(new[]
+                {
+                    MakeScene(starting.Id, starting.Name, "Edited starting"),
+                    MakeScene(brb.Id, brb.Name, "Edited BRB"),
+                }, null, null);
+            }
+
+            using (var reopened = new LayoutStore(path))
+            {
+                reopened.PrepareLayoutSnapshots("build-a");
+                Assert.True(reopened.RestoreAllDefaults());
+
+                var scenes = reopened.Load();
+                Assert.Equal("Factory starting", Assert.Single(scenes.Single(s => s.Name == SceneCatalog.Starting).Elements.OfType<Source>()).Name);
+                Assert.Equal("Factory BRB", Assert.Single(scenes.Single(s => s.Name == SceneCatalog.Brb).Elements.OfType<Source>()).Name);
+            }
+        }
+        finally
+        {
+            SqliteConnection.ClearAllPools();
+            try { File.Delete(path); } catch { /* best-effort cleanup */ }
+        }
+    }
+
     private static Scene MakeScene(string sourceName)
         => MakeScene(SceneCatalog.Starting, sourceName);