fix(Screenshot): allow region capture over shell overlays

quickshell/DMSShellIPC.qml

@@ -161,6 +161,21 @@ Item {
         target: "control-center"
     }
 
+    IpcHandler {
+        // Screenshot region-select handshake
+        function begin(): string {
+            PopoutManager.screenshotActive = true;
+            return "SCREENSHOT_MODE_ON";
+        }
+
+        function end(): string {
+            PopoutManager.screenshotActive = false;
+            return "SCREENSHOT_MODE_OFF";
+        }
+
+        target: "screenshot"
+    }
+
     IpcHandler {
         function resolveTabIndex(tab: string): int {
             switch ((tab || "").toLowerCase()) {