feat(text): persist independent text layer settings

Add additive defaults and round-trip tests for per-layer text content and formatting. Model the static text source after OBS text-source conventions: https://obsproject.com/kb/text-sources

ytLive.Tests/LayoutStorePersistenceTests.cs

@@ -15,6 +15,97 @@ namespace ytLive.Tests;
 /// </summary>
 public class LayoutStorePersistenceTests
 {
+    [Fact]
+    public void Text_Layers_RoundTrip_Independently_And_Legacy_Rows_Get_Defaults()
+    {
+        var path = Path.Combine(Path.GetTempPath(), $"ytLlive-layout-{Guid.NewGuid():N}.db");
+        try
+        {
+            var scene = new Scene { Name = "Starting" };
+            scene.Elements.Add(new Source
+            {
+                Name = "Headline",
+                Type = SourceType.TextOverlay,
+                TextContent = "First line\nSecond line",
+                TextFontFamily = "Arial",
+                TextFontSize = 72,
+                TextColor = "#12AB34",
+                TextBold = true,
+                TextAlignment = TextLayerAlignment.Center,
+            });
+            scene.Elements.Add(new Source
+            {
+                Name = "Caption",
+                Type = SourceType.TextOverlay,
+                TextContent = "Independent caption",
+                TextFontFamily = "Segoe UI",
+                TextFontSize = 24,
+                TextColor = "#80445566",
+                TextItalic = true,
+                TextUnderline = true,
+                TextAlignment = TextLayerAlignment.Right,
+            });
+
+            using (var store = new LayoutStore(path))
+                store.Save(new[] { scene }, null, null);
+
+            using (var reopened = new LayoutStore(path))
+            {
+                var sources = Assert.Single(reopened.Load()).Elements.OfType<Source>()
+                    .Where(source => source.Type == SourceType.TextOverlay).ToArray();
+                Assert.Equal(2, sources.Length);
+                Assert.Equal("First line\nSecond line", sources[0].TextContent);
+                Assert.Equal("Arial", sources[0].TextFontFamily);
+                Assert.Equal(72, sources[0].TextFontSize);
+                Assert.Equal("#12AB34", sources[0].TextColor);
+                Assert.True(sources[0].TextBold);
+                Assert.False(sources[0].TextItalic);
+                Assert.False(sources[0].TextUnderline);
+                Assert.Equal(TextLayerAlignment.Center, sources[0].TextAlignment);
+                Assert.Equal("Independent caption", sources[1].TextContent);
+                Assert.Equal(24, sources[1].TextFontSize);
+                Assert.Equal("#80445566", sources[1].TextColor);
+                Assert.False(sources[1].TextBold);
+                Assert.True(sources[1].TextItalic);
+                Assert.True(sources[1].TextUnderline);
+                Assert.Equal(TextLayerAlignment.Right, sources[1].TextAlignment);
+            }
+
+            SqliteConnection.ClearAllPools();
+            using (var raw = new SqliteConnection($"Data Source={path}"))
+            {
+                raw.Open();
+                using var cmd = raw.CreateCommand();
+                cmd.CommandText = "ALTER TABLE Source DROP COLUMN TextContent; ALTER TABLE Source DROP COLUMN TextFontFamily; ALTER TABLE Source DROP COLUMN TextFontSize; ALTER TABLE Source DROP COLUMN TextColor; ALTER TABLE Source DROP COLUMN TextBold; ALTER TABLE Source DROP COLUMN TextItalic; ALTER TABLE Source DROP COLUMN TextUnderline; ALTER TABLE Source DROP COLUMN TextAlignment;";
+                cmd.ExecuteNonQuery();
+            }
+            SqliteConnection.ClearAllPools();
+
+            using (var legacy = new LayoutStore(path))
+            {
+                var sources = Assert.Single(legacy.Load()).Elements.OfType<Source>()
+                    .Where(source => source.Type == SourceType.TextOverlay).ToArray();
+                Assert.Equal(2, sources.Length);
+                foreach (var source in sources)
+                {
+                    Assert.Equal("Text", source.TextContent);
+                    Assert.Equal("Segoe UI", source.TextFontFamily);
+                    Assert.Equal(48, source.TextFontSize);
+                    Assert.Equal("#FFFFFF", source.TextColor);
+                    Assert.False(source.TextBold);
+                    Assert.False(source.TextItalic);
+                    Assert.False(source.TextUnderline);
+                    Assert.Equal(TextLayerAlignment.Left, source.TextAlignment);
+                }
+            }
+        }
+        finally
+        {
+            SqliteConnection.ClearAllPools();
+            try { File.Delete(path); } catch { /* best-effort cleanup */ }
+        }
+    }
+
     /// <summary>TASK 47: the alert announcement display method must survive a
     /// restart. This one is easy to get quietly wrong — the Source row is read back
     /// by POSITIONAL index, so a column inserted anywhere but the end silently