fix: clear workflow when starting new project from welcome modal

When opening the welcome modal over an existing project and choosing
"New Project", the canvas now clears before showing the project setup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/WorkflowCanvas.tsx

@@ -265,7 +265,7 @@ const findScrollableAncestor = (target: HTMLElement, deltaX: number, deltaY: num
 };
 
 export function WorkflowCanvas() {
-  const { nodes, edges, groups, onNodesChange, onEdgesChange, onConnect, addNode, updateNodeData, loadWorkflow, getNodeById, addToGlobalHistory, setNodeGroupId, executeWorkflow, isModalOpen, showQuickstart, setShowQuickstart, navigationTarget, setNavigationTarget, captureSnapshot, applyEditOperations, setWorkflowMetadata, canvasNavigationSettings, setShortcutsDialogOpen, dimmedNodeIds, regenerateNode } =
+  const { nodes, edges, groups, onNodesChange, onEdgesChange, onConnect, addNode, updateNodeData, loadWorkflow, getNodeById, addToGlobalHistory, setNodeGroupId, executeWorkflow, isModalOpen, showQuickstart, setShowQuickstart, navigationTarget, setNavigationTarget, captureSnapshot, applyEditOperations, setWorkflowMetadata, canvasNavigationSettings, setShortcutsDialogOpen, dimmedNodeIds, regenerateNode, clearWorkflow } =
     useWorkflowStore();
   const openAnnotationModal = useAnnotationStore((state) => state.openModal);
   const { screenToFlowPosition, getViewport, zoomIn, zoomOut, setViewport, setCenter } = useReactFlow();
@@ -1912,6 +1912,7 @@ export function WorkflowCanvas() {
           }}
           onClose={() => setShowQuickstart(false)}
           onNewProject={() => {
+            clearWorkflow();
             setShowQuickstart(false);
             setShowNewProjectSetup(true);
           }}