fix(installer): use {autodesktop} for per-user desktop shortcut safety and fix IPersistFile 0x80070005 error

tests/Paca.Tests/App/DesktopGatewayDaemonCommandLineGateTests.cs

@@ -62,4 +62,21 @@ public class DesktopGatewayDaemonCommandLineGateTests
         Assert.Equal(52101, config.BeaconUdpPort);
         Assert.True(config.AutoStartUdpBeacon);
     }
+
+    [Fact]
+    public void Gate157_InstallerScript_MustUseAutoDesktop_And_MustNotContainCommonDesktop_ForPerUserSafety()
+    {
+        var installerPath = Path.Combine(SourceTree.Root, "build", "installer.iss");
+        Assert.True(File.Exists(installerPath), "installer.iss must exist");
+
+        var content = File.ReadAllText(installerPath);
+
+        // Standard user (PrivilegesRequired=lowest) has no write permission to {commondesktop} (C:\Users\Public\Desktop).
+        // Saving a shortcut to {commondesktop} throws IPersistFile::Save 0x80070005 (Access is Denied).
+        // It must use {autodesktop} which resolves to {userdesktop} for standard users.
+        Assert.DoesNotContain("{commondesktop}", content);
+        Assert.Contains("{autodesktop}\\{#APP_NAME}", content);
+        Assert.DoesNotContain("{commonprograms}", content);
+    }
 }
+