refactor: Introduce SketchTool base class and derived tool skeletons

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

src/LineTool.cpp

@@ -0,0 +1,51 @@
+#include "LineTool.h"
+#include "ViewportWidget.h"
+#include <QMouseEvent>
+#include <QKeyEvent>
+#include <QPainter>
+
+LineTool::LineTool(ViewportWidget* viewport)
+    : SketchTool(viewport)
+{
+}
+
+void LineTool::activate()
+{
+    m_isDefiningLine = false;
+    m_viewport->setProperty("dimensionInput", "");
+    m_viewport->setProperty("angleInput", "");
+    m_viewport->setProperty("dimensionEditMode", "length");
+    m_viewport->setProperty("isChainedLine", false);
+}
+
+void LineTool::deactivate()
+{
+    m_isDefiningLine = false;
+    m_viewport->setProperty("dimensionInput", "");
+    m_viewport->setProperty("angleInput", "");
+}
+
+void LineTool::mousePressEvent(QMouseEvent *event)
+{
+    // To be implemented
+}
+
+void LineTool::mouseMoveEvent(QMouseEvent *event)
+{
+    // To be implemented
+}
+
+void LineTool::keyPressEvent(QKeyEvent *event)
+{
+    // To be implemented
+}
+
+void LineTool::paintGL()
+{
+    // To be implemented
+}
+
+void LineTool::paint2D(QPainter& painter, const QMatrix4x4& modelView, const QMatrix4x4& projection)
+{
+    // To be implemented
+}