fix(#76): keep embedded Preview from stacking freshness notices

Weekend shell already discloses context availability; a second Preview banner
from shared championship headers produced conflicting Partial/Stale vocabulary.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/pages/RacePreviewPage.tsx

@@ -455,7 +455,8 @@ export function RacePreviewPage({
       data-meeting-key={previewMeeting.meeting_key}
       data-embedded={embedded ? 'true' : undefined}
     >
-      {dataNotice && (
+      {/* Weekend shell owns availability disclosure when Preview is embedded. */}
+      {!embedded && dataNotice && (
         <DataNotice
           availability={dataNotice}
           message={noticeMessage(dataNotice)}