feat: Manage active drawing tool state in controller and UI

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

src/ApplicationController.h

@@ -12,14 +12,24 @@ class ApplicationController : public QObject
 {
     Q_OBJECT
 public:
+    enum ToolType {
+        None,
+        Line,
+        Rectangle,
+        Circle
+    };
+    Q_ENUM(ToolType)
+
     explicit ApplicationController(QObject *parent = nullptr);
     ~ApplicationController();
 
     void setMainWindow(MainWindow* mainWindow);
     Document* document() const;
     SketchFeature* activeSketch() const;
+    ToolType activeTool() const;
 
 public slots:
+    void setActiveTool(ToolType tool);
     void newDocument();
     bool openDocument();
     bool saveDocument();
@@ -32,6 +42,7 @@ signals:
     void sketchModeStarted(ViewportWidget::SketchPlane plane);
     void sketchModeEnded();
     void currentFileChanged(const QString& path);
+    void activeToolChanged(ToolType tool);
 
 private:
     ApplicationController(const ApplicationController&) = delete;
@@ -43,6 +54,7 @@ private:
     QString m_currentFile;
     MainWindow* m_mainWindow = nullptr;
     SketchFeature* m_activeSketch = nullptr;
+    ToolType m_activeTool = ToolType::None;
 };
 
 #endif // APPLICATIONCONTROLLER_H