feat: Implement floating feature browser in viewport with transparent background

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

src/Document.h

@@ -19,12 +19,17 @@ public:
     bool save(const QString& path) const;
     bool load(const QString& path);
 
+    const QList<Feature*>& features() const;
+    void setFileName(const QString& fileName);
+    QString fileName() const;
+
 signals:
     void featureAdded(Feature* feature);
     void cleared();
 
 private:
     QList<Feature*> m_features;
+    QString m_fileName;
 };
 
 #endif // DOCUMENT_H