type: changed
area: stats

- Library groups now collapse multi-video series behind a per-group dropdown so the grid stays browsable.
- Sessions are rolled up per episode within each day, with a bulk delete that wipes every session in the group.
- Trends add a 365-day range next to the existing 7d/30d/90d/all options.
- Library detail view gets a delete-episode action that removes the video and all its sessions.
- Vocabulary Top 50 tightens the word/reading column so katakana entries no longer push the scores off screen.
- Episode detail hides card events whose Anki notes have been deleted, instead of showing phantom mining activity.
- Trend and watch-time charts share a unified theme with horizontal gridlines and larger ticks for legibility.