EANCH-WP-0004: HtmlViewer scroll parity and viewer-shell workplan

Export HtmlViewerAdapter from package root, add scrollRequestKey parity,
register finished workplan, update SCOPE.

src/index.ts

@@ -20,6 +20,20 @@ export {
   type CreateSelectorsOptions,
 } from "./selectors";
 
+// DOM adapter (re-exported from the src/dom/ boundary).
+export {
+  HtmlViewerAdapter,
+  resolveHtmlSelectors,
+  scrollToHtmlTarget,
+  renderHtmlHighlight,
+  captureFromRange,
+  domPathToNode,
+  nodeAtPath,
+  type HtmlViewerAdapterProps,
+  type HtmlViewerDebugOptions,
+  type StoredHtmlAnnotation,
+} from "./dom";
+
 // PDF adapter + helpers (re-exported from the src/pdf/ boundary).
 export {
   PdfViewerAdapter,