fix(recorder): add iframe support

apps/extension/src/shared/recording-document-identity.ts

@@ -0,0 +1,9 @@
+export const RECORD_DOCUMENT_ATTRIBUTE = "data-bsk-record-document";
+
+/** Read BrowserSkill's opaque per-Document recording identity from captured attributes. */
+export function readRecordingDocumentIdentity(
+  attrs: Readonly<Record<string, string>>,
+): string | undefined {
+  const identity = attrs[RECORD_DOCUMENT_ATTRIBUTE];
+  return identity ? identity : undefined;
+}