add dms-plugin-dev agent skill for plugin development (#2394)

.agents/skills/dms-plugin-dev/assets/templates/desktop/Widget.qml

@@ -0,0 +1,47 @@
+import QtQuick
+import qs.Common
+
+Item {
+    id: root
+
+    property var pluginService: null
+    property string pluginId: ""
+    property bool editMode: false
+    property real widgetWidth: 200
+    property real widgetHeight: 200
+    property real minWidth: 150
+    property real minHeight: 150
+
+    // TODO: Load settings reactively
+    property real bgOpacity: {
+        if (!pluginService) return 0.85
+        var val = pluginService.loadPluginData(pluginId, "opacity", 85)
+        return val / 100
+    }
+
+    Connections {
+        target: pluginService
+        function onPluginDataChanged(changedId) {
+            if (changedId !== pluginId) return
+            var val = pluginService.loadPluginData(pluginId, "opacity", 85)
+            bgOpacity = val / 100
+        }
+    }
+
+    Rectangle {
+        anchors.fill: parent
+        radius: Theme.cornerRadius
+        color: Theme.surfaceContainer
+        opacity: root.bgOpacity
+        border.color: root.editMode ? Theme.primary : "transparent"
+        border.width: root.editMode ? 2 : 0
+
+        // TODO: Add your widget content here
+        Text {
+            anchors.centerIn: parent
+            text: "Desktop Widget"
+            color: Theme.surfaceText
+            font.pixelSize: Theme.fontSizeLarge
+        }
+    }
+}