Repaint both heads in the v5 palette and embed its three fonts

tests/DodoSSH.Client.App.Layout.Tests/HeadlessApp.cs

@@ -41,8 +41,8 @@ internal static class HeadlessApp
     /// On a machine with no fonts at all it does not merely differ, it stops: <c>FontManager</c> throws
     /// "Default font family name can't be null or empty" during <c>AppBuilder.SetupUnsafe</c>, before any
     /// test body runs. That is how a container CI runner reports all sixty-eight of these as failures with
-    /// not one assertion among them. Naming Inter costs the runner nothing, because the font travels
-    /// inside the package rather than on the host.
+    /// not one assertion among them. Naming a font costs the runner nothing, because it travels inside the
+    /// package rather than on the host — true of Inter before this and of Montserrat now.
     /// </para>
     /// </remarks>
     public static AppBuilder BuildAvaloniaApp() =>
@@ -50,13 +50,27 @@ internal static class HeadlessApp
             .UseSkia()
             .UseHeadless(new AvaloniaHeadlessPlatformOptions { UseHeadlessDrawing = false })
             .WithInterFont()
-            .With(new FontManagerOptions { DefaultFamilyName = InterFamily });
+            .With(new FontManagerOptions
+            {
+                DefaultFamilyName = DefaultFamily,
+                FontFallbacks = [new FontFallback { FontFamily = new FontFamily(InterFamily) }],
+            });
 
-    /// <summary>The family <c>WithInterFont</c> registers.</summary>
+    /// <summary>The family <c>Program.BuildAvaloniaApp</c> asks the font manager to default to.</summary>
     /// <remarks>
     /// Kept in step with <c>Program.BuildAvaloniaApp</c> by hand, and it matters that they agree: a
     /// harness pinning a different default from the one the application runs with would certify heights
-    /// for a window nobody sees, which is the failure the opening paragraph of this file is about.
+    /// for a window nobody sees, which is the failure the opening paragraph of this file is about. It was
+    /// Inter until the v3 design; now it is Montserrat, embedded the same way, and Inter moves down to
+    /// <see cref="InterFamily"/> as the fallback both <c>BuildAvaloniaApp</c> methods name it as.
+    /// </remarks>
+    internal const string DefaultFamily = "avares://DodoSSH.Client.Shell/Assets/Fonts#Montserrat";
+
+    /// <summary>The family <c>WithInterFont</c> registers.</summary>
+    /// <remarks>
+    /// No longer the default — see <see cref="DefaultFamily"/> — but still registered and still named
+    /// here, because it is still the fallback both heads' <c>BuildAvaloniaApp</c> fall back to, and a test
+    /// measuring a glyph Montserrat does not cover has to fall back to the same font the application does.
     /// </remarks>
     internal const string InterFamily = "avares://Avalonia.Fonts.Inter/Assets#Inter";
 }