feat(m1): 应用骨架、传送门面板与暂存区

- CMake 构建（Qt6 + dtk2widget + LayerShellQt）
- 单实例 / --daemon / --show
- DBlur 双栏面板：传送门 + 暂存区，layer-shell 定位，不抢焦点
- 暂存区模型：文件/文字/图片、去重、JSON 持久化、文件消失清理
- 列表委托：复选框、缩略图、名称、hover 关闭按钮
- 全选 / 反选 / 删除选中
- 应用图标（多尺寸 hicolor）与 desktop 入口
- 方案更新：确认 layer-shell + 遮挡自动隐藏

src/ui/portalpanel.h

@@ -0,0 +1,56 @@
+// SPDX-FileCopyrightText: 2026 GXDE OS Team
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <DBlurEffectWidget>
+#include <QWidget>
+
+class QLabel;
+class QPushButton;
+class PortalZone;
+class StagingModel;
+class StagingView;
+
+/**
+ * The floating staging panel (传送门 + 暂存区).
+ *
+ * On Wayland this is a layer-shell overlay surface so that it does not appear
+ * in the dock, does not steal keyboard focus and can be positioned exactly.
+ * On X11 it falls back to a frameless tool window placed bottom-right.
+ */
+class PortalPanel : public Dtk::Widget::DBlurEffectWidget
+{
+    Q_OBJECT
+
+public:
+    explicit PortalPanel(StagingModel *model, QWidget *parent = nullptr);
+    ~PortalPanel() override;
+
+    void refreshLayout();
+    void popup();
+    void dismiss();
+
+signals:
+    void openChatRequested();
+
+protected:
+    void showEvent(QShowEvent *event) override;
+
+private:
+    void setupUi();
+    void setupWindow();
+    void updateGeometryForContent();
+    void updateSelectionBar();
+
+    StagingModel *m_model = nullptr;
+    StagingView *m_view = nullptr;
+    PortalZone *m_zone = nullptr;
+    QWidget *m_header = nullptr;
+    QWidget *m_selectionBar = nullptr;
+    QWidget *m_factory = nullptr;
+    QLabel *m_countLabel = nullptr;
+    QPushButton *m_selectAllButton = nullptr;
+    QPushButton *m_invertButton = nullptr;
+    QPushButton *m_deleteButton = nullptr;
+};