fix: Add and emit toolDeactivated signal in ViewportWidget

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

src/ViewportWidget.cpp

@@ -453,6 +453,7 @@ void ViewportWidget::keyPressEvent(QKeyEvent *event)
     if (event->key() == Qt::Key_Escape) {
         if (m_isDefiningLine) {
             m_isDefiningLine = false;
+            emit toolDeactivated();
             update();
             return;
         }

src/ViewportWidget.h

@@ -47,6 +47,7 @@ public slots:
 signals:
     void lineAdded(const gp_Pnt& start, const gp_Pnt& end);
     void planeSelected(SketchPlane plane);
+    void toolDeactivated();
 
 protected:
     void initializeGL() override;