fix(docs): demo page still imported the react-pdf exporter from the package root

The /demo page (outside the generated example trees) kept the old root
import; local builds masked it by resolving a stale workspace dist. Point
it at the deprecated /react-pdf subpath - migrating the demo's PDF action
to the Typst-based PDFExporter rides the examples/docs follow-up pass.

Author: YousefED

docs/app/demo/_components/DemoEditor.tsx

@@ -44,10 +44,12 @@ import {
   ODTExporter,
   odtDefaultSchemaMappings,
 } from "@blocknote/xl-odt-exporter";
+// The deprecated react-pdf exporter; the demo's PDF action migrates to the
+// Typst-based PDFExporter with the examples/docs pass for the new API.
 import {
   PDFExporter,
   pdfDefaultSchemaMappings,
-} from "@blocknote/xl-pdf-exporter";
+} from "@blocknote/xl-pdf-exporter/react-pdf";
 import { pdf } from "@react-pdf/renderer";
 import { DefaultChatTransport } from "ai";
 import { useTheme } from "next-themes";