Initial commit: .NET MAUI Linux Platform

Complete Linux platform implementation for .NET MAUI with:

- 35+ Skia-rendered controls (Button, Label, Entry, CarouselView, etc.)
- Platform services (Clipboard, FilePicker, Notifications, DragDrop, etc.)
- Accessibility support (AT-SPI2, High Contrast)
- HiDPI and Input Method support
- 216 unit tests
- CI/CD workflows
- Project templates
- Documentation

🤖 Generated with Claude Code

tests/Views/SkiaButtonTests.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using FluentAssertions;
+using Microsoft.Maui.Platform;
+using SkiaSharp;
+using Xunit;
+
+namespace Microsoft.Maui.Controls.Linux.Tests.Views;
+
+public class SkiaButtonTests
+{
+    [Fact]
+    public void Constructor_SetsDefaultValues()
+    {
+        // Arrange & Act
+        var button = new SkiaButton();
+
+        // Assert
+        button.Text.Should().BeEmpty();
+        button.IsEnabled.Should().BeTrue();
+        button.IsFocusable.Should().BeTrue();
+    }
+
+    [Fact]
+    public void Text_WhenSet_UpdatesProperty()
+    {
+        // Arrange
+        var button = new SkiaButton();
+
+        // Act
+        button.Text = "Click Me";
+
+        // Assert
+        button.Text.Should().Be("Click Me");
+    }
+
+    [Fact]
+    public void Measure_ReturnsMinimumSize()
+    {
+        // Arrange
+        var button = new SkiaButton { Text = "Test" };
+
+        // Act
+        var size = button.Measure(new SKSize(1000, 1000));
+
+        // Assert
+        size.Width.Should().BeGreaterThan(0);
+        size.Height.Should().BeGreaterThan(0);
+    }
+
+    [Fact]
+    public void Measure_ReturnsPositiveSize()
+    {
+        // Arrange
+        var button = new SkiaButton
+        {
+            Text = "Test",
+            RequestedWidth = 200,
+            RequestedHeight = 50
+        };
+
+        // Act
+        var size = button.Measure(new SKSize(1000, 1000));
+
+        // Assert - Measure returns content-based size
+        size.Width.Should().BeGreaterThan(0);
+        size.Height.Should().BeGreaterThan(0);
+    }
+
+    [Fact]
+    public void IsEnabled_WhenFalse_UpdatesProperty()
+    {
+        // Arrange
+        var button = new SkiaButton { Text = "Test" };
+
+        // Act
+        button.IsEnabled = false;
+
+        // Assert
+        button.IsEnabled.Should().BeFalse();
+    }
+
+    [Fact]
+    public void Clicked_EventCanBeSubscribed()
+    {
+        // Arrange
+        var button = new SkiaButton { Text = "Test" };
+        var eventSubscribed = false;
+
+        // Act
+        button.Clicked += (s, e) => eventSubscribed = true;
+
+        // Assert - Just verify we can subscribe without error
+        eventSubscribed.Should().BeFalse(); // Not raised yet, just subscribed
+    }
+
+    [Fact]
+    public void Draw_DoesNotThrow()
+    {
+        // Arrange
+        var button = new SkiaButton { Text = "Test" };
+        button.Bounds = new SKRect(0, 0, 100, 40);
+
+        using var surface = SKSurface.Create(new SKImageInfo(200, 100));
+        var canvas = surface.Canvas;
+
+        // Act & Assert
+        var exception = Record.Exception(() => button.Draw(canvas));
+        exception.Should().BeNull();
+    }
+
+    [Fact]
+    public void TextColor_WhenSet_UpdatesProperty()
+    {
+        // Arrange
+        var button = new SkiaButton();
+        var color = new SKColor(255, 0, 0);
+
+        // Act
+        button.TextColor = color;
+
+        // Assert
+        button.TextColor.Should().Be(color);
+    }
+
+    [Fact]
+    public void BackgroundColor_WhenSet_UpdatesProperty()
+    {
+        // Arrange
+        var button = new SkiaButton();
+        var color = new SKColor(0, 255, 0);
+
+        // Act
+        button.BackgroundColor = color;
+
+        // Assert
+        button.BackgroundColor.Should().Be(color);
+    }
+}