2d675aa35d
practice/deck_list returns the same wire shape as /deck/info (the client parses both via DeckGroupListData), but only ever sent user decks — so a fresh account saw no default decks and couldn't start a practice match. Extract the /deck/info hydration into a shared IDeckListBuilder used by /deck/info, /deck/my_list, and /practice/deck_list. Practice passes padEmptySlots:false (deck *select*, not builder) — matches the prod practice capture, which returns real decks unpadded plus the 8 per-class default decks and per-class leader-skin settings. Retire the near-duplicate PracticeDeckListResponse DTO in favor of the shared DeckListResponse. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>