fix(stats): address CodeRabbit review on PR #50

- Guard episode deletion against double-submit with an isDeletingRef +
  setIsDeleting pair threaded through buildDeleteEpisodeHandler, and
  disable the MediaHeader delete button while a request is in flight.
- Restore MediaHeader title truncation by adding min-w-0 flex-1 to the
  h2 so long titles shrink instead of pushing the delete button away.
- Normalize the headword in FrequencyRankTable before comparing it to
  the (hiragana-normalized) reading so katakana-only entries like カレー
  no longer render a redundant 【かれー】. Test strengthened to reject
  any bracketed reading, not just the literal.
- Rewrite confirmBucketDelete copy to include the "and all associated
  data" warning and handle singular/plural cleanly.
- Run Prettier across the stats files CI was complaining about
  (EpisodeDetail, WatchTimeChart, SessionsTab + test, FrequencyRankTable
  + test, session-grouping test) to clear the format:check:stats gate.

stats/src/lib/delete-confirm.ts

@@ -19,7 +19,12 @@ export function confirmEpisodeDelete(title: string): boolean {
 }
 
 export function confirmBucketDelete(title: string, count: number): boolean {
+  if (count === 1) {
+    return globalThis.confirm(
+      `Delete this session of "${title}" from this day and all associated data?`,
+    );
+  }
   return globalThis.confirm(
-    `Delete all ${count} session${count === 1 ? '' : 's'} of "${title}" from this day?`,
+    `Delete all ${count} sessions of "${title}" from this day and all associated data?`,
   );
 }