feat(app): add --simulate flag for headless demo captures

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/app/MainWindow.cpp

@@ -229,6 +229,11 @@ void MainWindow::loadSample()
     m_view->zoomToFit();
 }
 
+void MainWindow::setSimulationRunning(bool running)
+{
+    m_simulateAction->setChecked(running);
+}
+
 void MainWindow::runSimulation(bool enabled)
 {
     if (enabled) {

src/app/MainWindow.h

@@ -22,6 +22,7 @@ public:
     NetworkModel* model() const { return m_model; }
 
     void loadSample();
+    void setSimulationRunning(bool running);
 
 protected:
     void closeEvent(QCloseEvent* event) override;

src/main.cpp

@@ -14,6 +14,8 @@ int main(int argc, char** argv)
     const QStringList args = app.arguments();
     if (args.contains(QStringLiteral("--sample")))
         window.loadSample();
+    if (args.contains(QStringLiteral("--simulate")))
+        window.setSimulationRunning(true);
 
     // Headless smoke check: --screenshot <file.png> renders and exits.
     const int shotIdx = args.indexOf(QStringLiteral("--screenshot"));