feat(ads/seo/release): v1.2.0 with live Google Ads, isolated ad profile, ads.txt, and SEO/AEO/GEO optimization

tests/Paca.Tests/App/MultiDisplayLayoutEngineGateTests.cs

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+using System;
+using System.Collections.Generic;
+using System.Windows;
+using Paca.App.Core;
+using Xunit;
+
+namespace Paca.Tests.App;
+
+public class MultiDisplayLayoutEngineGateTests
+{
+    [Fact]
+    public void Gate269_MultiDisplayLayoutEngine_ClampsWindow_WithinSingleMonitorBounds()
+    {
+        var workArea = new Rect(0, 0, 1920, 1080);
+        // Window 400x300 requested at (1800, 950) -> exceeds 1920 and 1080
+        var clamped = MultiDisplayLayoutEngine.ClampToWorkArea(
+            requestedLeft: 1800,
+            requestedTop: 950,
+            windowWidth: 400,
+            windowHeight: 300,
+            workArea: workArea,
+            margin: 16
+        );
+
+        Assert.Equal(1920 - 400 - 16, clamped.X);
+        Assert.Equal(1080 - 300 - 16, clamped.Y);
+    }
+
+    [Fact]
+    public void Gate270_MultiDisplayLayoutEngine_HandlesNegativeCoordinates_OnSecondaryLeftMonitor()
+    {
+        var leftMonitorWorkArea = new Rect(-1920, 0, 1920, 1080);
+        
+        // Window 400x300 requested at -2000 (beyond left edge)
+        var clamped = MultiDisplayLayoutEngine.ClampToWorkArea(
+            requestedLeft: -2000,
+            requestedTop: 100,
+            windowWidth: 400,
+            windowHeight: 300,
+            workArea: leftMonitorWorkArea,
+            margin: 16
+        );
+
+        Assert.Equal(-1920 + 16, clamped.X);
+        Assert.Equal(100, clamped.Y);
+    }
+
+    [Fact]
+    public void Gate271_MultiDisplayLayoutEngine_ConvertsDpiToDips()
+    {
+        // Standard 96 DPI = 1.0 scale
+        Assert.Equal(100.0, MultiDisplayLayoutEngine.PixelsToDips(100, 96));
+
+        // 144 DPI (150% scaling) -> 150 pixels = 100 DIPs
+        Assert.Equal(100.0, MultiDisplayLayoutEngine.PixelsToDips(150, 144));
+    }
+
+    [Fact]
+    public void Gate272_MultiDisplayLayoutEngine_FindsBestScreen_ForWindow()
+    {
+        var screens = new List<Rect>
+        {
+            new(0, 0, 1920, 1080),       // Primary screen
+            new(1920, 0, 1920, 1080)     // Secondary screen to the right
+        };
+
+        // Window placed mostly on secondary screen (e.g. x=2000)
+        var bestScreen = MultiDisplayLayoutEngine.FindBestScreen(new Rect(2000, 200, 400, 300), screens);
+        Assert.Equal(1920, bestScreen.X);
+    }
+}