Close desktop safety gaps

config/dot/quickshell/displays-harness.qml

@@ -6,6 +6,10 @@ import qs.config
 import qs.services
 
 ShellRoot {
+    // The isolated screen model begins with both fixture outputs so changing
+    // it below exercises the same reactive topology path as a real hotplug.
+    Component.onCompleted: Displays.screenOverride = ["DP-2", "HDMI-A-1"]
+
     IpcHandler {
         target: "displays-test"
 
@@ -42,6 +46,7 @@ ShellRoot {
         function transactionStatus(): string {
             return JSON.stringify({
                 layout: Displays.currentLayout(),
+                primaryFirst: Displays.primaryFirstMonitors.map(monitor => monitor.name),
                 pending: Displays.pendingRequestedLayout,
                 previous: Displays.pendingPreviousLayout,
                 reverting: Displays.revertExpectedLayout,
@@ -141,5 +146,8 @@ ShellRoot {
             if (monitor) Displays.forget(monitor.name);
         }
         function refresh(): void { Displays.refresh(); }
+        function setScreenModel(names: string): void {
+            Displays.screenOverride = JSON.parse(names);
+        }
     }
 }