Migrate Terminal theme and tests added on main to Terminal.Gui 2.4.5

Rebasing onto main brought in the Terminal theme (#176) and its tests,
which were written against Terminal.Gui 2.0:

- TerminalTheme: ColorScheme -> Scheme; drop the local Attribute alias
  now provided by GlobalUsings.
- ThemeManager: Application.Force16Colors no longer exists as a static;
  set the flag on Application.Driver only.
- ThemeManagerTests: assert UseTerminalColors on the theme since the
  driver (which now owns Force16Colors) is null in headless tests.
- ThemeSchemeTests: ThemeStyler.ApplyTo was dropped in favour of main's
  leaner surface (#177); test ApplyToFrame instead.

Author: claude

App/Themes/TerminalTheme.cs

@@ -1,5 +1,4 @@
 using Terminal.Gui;
-using Attribute = Terminal.Gui.Attribute;
 
 namespace Opcilloscope.App.Themes;
 
@@ -82,10 +81,10 @@ public class TerminalTheme : AppTheme
 
     // Override color schemes - focus highlight uses a DarkGray band since
     // panel-background shades are not available in the 16-color palette
-    private ColorScheme? _mainColorScheme;
-    private ColorScheme? _menuColorScheme;
+    private Scheme? _mainColorScheme;
+    private Scheme? _menuColorScheme;
 
-    public override ColorScheme MainColorScheme => _mainColorScheme ??= new()
+    public override Scheme MainColorScheme => _mainColorScheme ??= new()
     {
         Normal = NormalAttr,
         Focus = new Attribute(ForegroundBright, new Color(ColorName16.DarkGray)),
@@ -94,7 +93,7 @@ public class TerminalTheme : AppTheme
         Disabled = new Attribute(StatusInactive, Background)
     };
 
-    public override ColorScheme MenuColorScheme => _menuColorScheme ??= new()
+    public override Scheme MenuColorScheme => _menuColorScheme ??= new()
     {
         Normal = NormalAttr,
         Focus = new Attribute(Background, Foreground),  // Inverted for menu focus

App/Themes/ThemeManager.cs

@@ -82,10 +82,8 @@ public static void SetTheme(AppTheme theme)
     /// </summary>
     private static void ApplyTerminalColorMode(AppTheme theme)
     {
-        Application.Force16Colors = theme.UseTerminalColors;
-
-        // The v2 facade driver caches its own flag rather than reading
-        // Application.Force16Colors, so propagate explicitly when running
+        // Terminal.Gui 2.4 removed the static Application.Force16Colors;
+        // the flag now lives on the driver itself.
         if (Application.Driver is { } driver)
         {
             driver.Force16Colors = theme.UseTerminalColors;

Tests/Opcilloscope.Tests/App/ThemeManagerTests.cs

@@ -123,22 +123,25 @@ public void ThemeManager_SetThemeByName_WithInvalidName_DoesNothing()
     }
 
     [Fact]
-    public void ThemeManager_SetTerminalTheme_TogglesForce16Colors()
+    public void ThemeManager_SetTerminalTheme_TogglesTerminalColorMode()
     {
+        // Terminal.Gui 2.4 removed the static Application.Force16Colors; the flag now
+        // lives on Application.Driver, which is null in headless tests. Assert on the
+        // theme property that ThemeManager propagates to the driver when one exists.
         try
         {
             // Act - Terminal theme enables 16-color ANSI output
             ThemeManager.SetTheme("Terminal");
 
             // Assert
             Assert.IsType<TerminalTheme>(ThemeManager.Current);
-            Assert.True(Terminal.Gui.Application.Force16Colors);
+            Assert.True(ThemeManager.Current.UseTerminalColors);
 
             // Act - switching back restores 24-bit color output
             ThemeManager.SetTheme("Dark");
 
             // Assert
-            Assert.False(Terminal.Gui.Application.Force16Colors);
+            Assert.False(ThemeManager.Current.UseTerminalColors);
         }
         finally
         {

Tests/Opcilloscope.Tests/Tui/ThemeSchemeTests.cs

@@ -38,12 +38,12 @@ public void ButtonScheme_IsADistinctScheme(AppTheme theme)
     }
 
     [Fact]
-    public void ThemeStyler_ApplyTo_SetsTheViewScheme()
+    public void ThemeStyler_ApplyToFrame_SetsTheViewScheme()
     {
         var theme = new DarkTheme();
-        var view = new View();
+        var view = new FrameView();
 
-        ThemeStyler.ApplyTo(view, theme);
+        ThemeStyler.ApplyToFrame(view, theme);
 
         Scheme? applied = view.GetScheme();
         Assert.NotNull(applied);