Add defensive createdAt insertion on frontend

Add ensureCreatedAt() helper that defaults to 2025-01-01 if backend
violates the createdAt guarantee. Applied to all metadata loading paths:
- workspace.list()
- workspace.onMetadata() updates
- workspace.getInfo() after rename
- workspace fork switch event

This prevents crashes if backend contract is violated.

Author: ammar-agent

src/App.tsx

@@ -639,6 +639,14 @@ function AppInner() {
         return;
       }
 
+      // DEFENSIVE: Ensure createdAt exists
+      if (!workspaceInfo.createdAt) {
+        console.warn(
+          `[Frontend] Workspace ${workspaceInfo.id} missing createdAt in fork switch - using default (2025-01-01)`
+        );
+        workspaceInfo.createdAt = "2025-01-01T00:00:00.000Z";
+      }
+
       // Update metadata Map immediately (don't wait for async metadata event)
       // This ensures the title bar effect has the workspace name available
       setWorkspaceMetadata((prev) => {

src/hooks/useWorkspaceManagement.ts

@@ -10,6 +10,20 @@ interface UseWorkspaceManagementProps {
   onSelectedWorkspaceUpdate: (workspace: WorkspaceSelection | null) => void;
 }
 
+/**
+ * Ensure workspace metadata has createdAt timestamp.
+ * DEFENSIVE: Backend guarantees createdAt, but default to 2025-01-01 if missing.
+ * This prevents crashes if backend contract is violated.
+ */
+function ensureCreatedAt(metadata: FrontendWorkspaceMetadata): void {
+  if (!metadata.createdAt) {
+    console.warn(
+      `[Frontend] Workspace ${metadata.id} missing createdAt - using default (2025-01-01)`
+    );
+    metadata.createdAt = "2025-01-01T00:00:00.000Z";
+  }
+}
+
 /**
  * Hook to manage workspace operations (create, remove, rename, list)
  */
@@ -28,6 +42,7 @@ export function useWorkspaceManagement({
       const metadataList = await window.api.workspace.list();
       const metadataMap = new Map();
       for (const metadata of metadataList) {
+        ensureCreatedAt(metadata);
         // Use stable workspace ID as key (not path, which can change)
         metadataMap.set(metadata.id, metadata);
       }
@@ -62,6 +77,7 @@ export function useWorkspaceManagement({
             // Workspace deleted - remove from map
             updated.delete(event.workspaceId);
           } else {
+            ensureCreatedAt(event.metadata);
             updated.set(event.workspaceId, event.metadata);
           }
 
@@ -169,6 +185,7 @@ export function useWorkspaceManagement({
             // Get updated workspace metadata from backend
             const newMetadata = await window.api.workspace.getInfo(newWorkspaceId);
             if (newMetadata) {
+              ensureCreatedAt(newMetadata);
               onSelectedWorkspaceUpdate({
                 projectPath: selectedWorkspace.projectPath,
                 projectName: newMetadata.projectName,