feat: Implement floating feature browser in viewport with transparent background

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

src/Document.cpp

@@ -3,6 +3,7 @@
 #include "SketchFeature.h"
 
 #include <QFile>
+#include <QFileInfo>
 #include <QJsonDocument>
 #include <QJsonArray>
 #include <QJsonObject>
@@ -26,9 +27,28 @@ void Document::clear()
 {
     qDeleteAll(m_features);
     m_features.clear();
+    m_fileName.clear();
     emit cleared();
 }
 
+const QList<Feature*>& Document::features() const
+{
+    return m_features;
+}
+
+void Document::setFileName(const QString& fileName)
+{
+    m_fileName = fileName;
+}
+
+QString Document::fileName() const
+{
+    if (m_fileName.isEmpty()) {
+        return "Untitled";
+    }
+    return QFileInfo(m_fileName).fileName();
+}
+
 bool Document::save(const QString& path) const
 {
     QJsonArray featuresArray;