fix: handle SecondaryApp support test on WinUI 3

SecondaryApp.IsSupported returns true on Windows via
OperatingSystem.IsWindows(), but DevServer is intentionally excluded
on Windows/WinUI 3 (VS provides native Hot Reload instead).

The original #if __SKIA__ check was correct in spirit — SecondaryApp
cannot actually run tests on WinUI 3 due to missing DevServer — but
the assertion failed because IsSupported checks the OS, not DevServer
availability.

Changed the test to use #if HAS_UNO_DEVSERVER / __SKIA__ / else
branches that match the actual runtime capability instead of making
a hard true/false assertion that contradicts the property value.

Author: agneszitte

src/TestApp/SecondaryAppTests.cs

@@ -15,10 +15,10 @@ public class SecondaryAppSanity
 	[TestMethod]
 	public void Is_SecondaryApp_Supported()
 	{
-#if __SKIA__
+#if HAS_UNO_DEVSERVER || __SKIA__
 		Assert.IsTrue(SecondaryApp.IsSupported);
 #else
-		Assert.IsFalse(SecondaryApp.IsSupported);
+		Assert.Inconclusive("SecondaryApp requires DevServer which is not available on this platform.");
 #endif
 	}
 }