feat: Introduce PreviewContext and document a new spatial workspace architecture.

frontend/src/app/DocumentsRoute.tsx

@@ -4,6 +4,7 @@ import { useNavigate } from 'react-router-dom';
 import {
   DocumentsFilterProvider,
 } from '../documents/context/DocumentsFilterContext';
+import { PreviewProvider } from '../preview/PreviewContext';
 import { useWorkspaceSurface } from './useWorkspaceSurface';
 import { DocumentsHeaderBreadcrumb } from '../documents/panel/DocumentsPanelHeader';
 import { SidebarProvider, useSidebarContext } from '../sidebar/SidebarContext';
@@ -75,7 +76,9 @@ const DocumentsRouteContent: React.FC = () => {
   const content = renderSurface();
   return (
     <DocumentsFilterProvider value={documentsFilter}>
-      {content}
+      <PreviewProvider ensureDownloadUrl={surfaceConfig.documentsTableProps?.ensureDownloadUrl}>
+        {content}
+      </PreviewProvider>
     </DocumentsFilterProvider>
   );
 };