ready screen: hide READY! text after first drive, reset on ignition cycle

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

selfdrive/ui/qt/home.cc

@@ -98,6 +98,7 @@ void HomeWindow::updateState(const UIState &s) {
     } else if (!parked && was_parked_onroad) {
       LOGW("CLP UI: drive transition -> showing onroad");
       slayout->setCurrentWidget(onroad);
+      ready->has_driven = true;
     }
     was_parked_onroad = parked;