feat(mosstank): add VTank-style automation PoC

src/AcDream.App/UI/UiMarkupTabButton.cs

@@ -0,0 +1,47 @@
+using System.Numerics;
+
+namespace AcDream.App.UI;
+
+/// <summary>
+/// Compact KSML tab used by plugin windows. It deliberately uses the retained
+/// input/font path and VTank's text-strip presentation rather than introducing
+/// a plugin-owned renderer.
+/// </summary>
+public sealed class UiMarkupTabButton : UiSimpleButton
+{
+    private static readonly Vector4 ActiveText =
+        new(0.94f, 0.76f, 0.18f, 1f);
+    private static readonly Vector4 NormalText =
+        new(0.78f, 0.76f, 0.67f, 1f);
+    private static readonly Vector4 DisabledText =
+        new(0.34f, 0.33f, 0.29f, 1f);
+    private static readonly Vector4 Underline =
+        new(0.77f, 0.59f, 0.12f, 1f);
+
+    public Func<bool>? SelectedSource { get; set; }
+
+    public bool IsSelected => SelectedSource?.Invoke() ?? false;
+
+    public UiMarkupTabButton()
+    {
+        BackgroundColor = Vector4.Zero;
+        BorderColor = Vector4.Zero;
+        BorderThickness = 0f;
+        Outline = true;
+    }
+
+    protected override void OnTick(double deltaSeconds)
+    {
+        base.OnTick(deltaSeconds);
+        TextColor = !Enabled
+            ? DisabledText
+            : IsSelected ? ActiveText : NormalText;
+    }
+
+    protected override void OnDraw(UiRenderContext ctx)
+    {
+        base.OnDraw(ctx);
+        if (IsSelected)
+            ctx.DrawFill(2f, Height - 2f, MathF.Max(0f, Width - 4f), 1f, Underline);
+    }
+}