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/staging/stagingmodel.h

@@ -0,0 +1,76 @@
+// SPDX-FileCopyrightText: 2026 GXDE OS Team
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#pragma once
+
+#include <QAbstractListModel>
+#include <QFileIconProvider>
+#include <QHash>
+#include <QIcon>
+#include <QTimer>
+
+#include "stagingitem.h"
+
+class QMimeData;
+
+/**
+ * Model backing the staging area.
+ *
+ * Entries are persisted as JSON in the application data directory and entries
+ * whose backing file disappeared are pruned periodically.
+ */
+class StagingModel : public QAbstractListModel
+{
+    Q_OBJECT
+
+public:
+    enum Roles {
+        TypeRole = Qt::UserRole + 1,
+        IdRole,
+        NameRole,
+        UriRole,
+        TextRole,
+        CheckedRole,
+        ExistsRole,
+        IconRole,
+    };
+
+    explicit StagingModel(QObject *parent = nullptr);
+    ~StagingModel() override;
+
+    int rowCount(const QModelIndex &parent = QModelIndex()) const override;
+    QVariant data(const QModelIndex &index, int role = Qt::DisplayRole) const override;
+    bool removeRows(int row, int count, const QModelIndex &parent = QModelIndex()) override;
+    Qt::ItemFlags flags(const QModelIndex &index) const override;
+
+    void addMimeData(const QMimeData *mimeData, int *addedRow = nullptr);
+    void addFiles(const QStringList &localPaths, int *addedRow = nullptr);
+    void addText(const QString &text, int *addedRow = nullptr);
+    void addImage(const QImage &image, int *addedRow = nullptr);
+
+    void setChecked(int row, bool checked);
+    void clearAll();
+
+    const StagingItem *itemAt(int row) const;
+    bool isEmpty() const { return m_items.isEmpty(); }
+    int count() const { return m_items.size(); }
+
+    void load();
+    void save() const;
+
+signals:
+    void countChanged();
+    void itemAdded(int row);
+
+private:
+    void insertItem(const StagingItem &item, int *addedRow);
+    QIcon iconFor(const StagingItem &item) const;
+    QString imageCacheDir() const;
+    void pruneMissing();
+
+    QList<StagingItem> m_items;
+    QTimer m_pruneTimer;
+    mutable QHash<QString, QIcon> m_iconCache;
+    mutable QFileIconProvider m_iconProvider;
+    QString m_storePath;
+};