fix: add defensive null checks to prevent filter crash

- Add fallback to empty arrays for toolTypes, configs, and folders
- Handle undefined API responses gracefully
- Prevent Cannot read properties of undefined (reading 'filter') error

Quality gates: npm run build passed

apps/web/src/pages/tool-workshop.tsx

@@ -89,9 +89,9 @@ export const ToolWorkshopPage = () => {
   const [showFolderForm, setShowFolderForm] = useState(false);
   const [selectedFolder, setSelectedFolder] = useState<ConfigFolder | null>(null);
 
-  const selectedToolType = toolTypes.find((t) => t.id === selectedToolTypeId) || null;
-  const toolConfigs = configs.filter((c) => c.tool_type_id === selectedToolTypeId);
-  const toolFolders = folders; // Config folders are global, not per-tool-type in current API
+  const selectedToolType = (toolTypes || []).find((t) => t.id === selectedToolTypeId) || null;
+  const toolConfigs = (configs || []).filter((c) => c.tool_type_id === selectedToolTypeId);
+  const toolFolders = folders || []; // Config folders are global, not per-tool-type in current API
 
   const loadData = useCallback(async () => {
     setStatus("loading");
@@ -101,9 +101,9 @@ export const ToolWorkshopPage = () => {
         listToolConfigs(),
         listConfigFolders(),
       ]);
-      setToolTypes(types);
-      setConfigs(cfgs);
-      setFolders(fldrs);
+      setToolTypes(types || []);
+      setConfigs(cfgs || []);
+      setFolders(fldrs || []);
       setStatus("ready");
     } catch {
       setStatus("error");