fix: Let notification center use Wayland exclusive zones

The Wayland notification center panel should rely on compositor-reserved exclusive zones rather than adding Dock margins itself.
- Add a layer-shell margin helper that returns zero on Wayland and preserves windowMargin() elsewhere.
- Set exclusionZone to 0 on Wayland and keep -1 for non-Wayland platforms.
- Avoid extra Dock spacing on Wayland without changing X11 behavior.

Wayland 通知中心面板应依赖合成器预留的独占区域，而不是自身继续叠加 Dock 边距。
- 增加 layer-shell 边距辅助函数，在 Wayland 下返回 0，其他平台继续使用 windowMargin()。
- Wayland 下将 exclusionZone 设置为 0，非 Wayland 平台保持 -1。
- 避免 Wayland 下出现额外 Dock 间距，同时不改变 X11 行为。

Log: Let notification center use Wayland exclusive zones
Pms: BUG-365785

Author: yixinshark

panels/notification/center/package/main.qml

@@ -81,6 +81,13 @@ Window {
         }
     }
 
+    function layerShellMargin(position) {
+        if (Qt.platform.pluginName === "wayland")
+            return 0
+
+        return windowMargin(position)
+    }
+
     // visible: true
     visible: Panel.visible
     flags: Qt.Tool
@@ -90,10 +97,10 @@ Window {
     // height: 800
     DLayerShellWindow.layer: DLayerShellWindow.LayerOverlay
     DLayerShellWindow.anchors: DLayerShellWindow.AnchorRight | DLayerShellWindow.AnchorTop | DLayerShellWindow.AnchorBottom
-    DLayerShellWindow.topMargin: windowMargin(0) + contentPadding
-    DLayerShellWindow.rightMargin: windowMargin(1) + contentPadding
-    DLayerShellWindow.bottomMargin: windowMargin(2) + contentPadding
-    DLayerShellWindow.exclusionZone: -1
+    DLayerShellWindow.topMargin: layerShellMargin(0) + contentPadding
+    DLayerShellWindow.rightMargin: layerShellMargin(1) + contentPadding
+    DLayerShellWindow.bottomMargin: layerShellMargin(2) + contentPadding
+    DLayerShellWindow.exclusionZone: Qt.platform.pluginName === "wayland" ? 0 : -1
     DLayerShellWindow.keyboardInteractivity: DLayerShellWindow.KeyboardInteractivityOnDemand
     palette: DTK.palette
     ColorSelector.family: Palette.CrystalColor