Warm boss card art in battle (GPU free post-draft) so boss plays show art instantly

ui.py

@@ -385,9 +385,11 @@ def battle_opening_steps(
     )
     draw_cards(duel.player, OPENING_HAND_SIZE)
     draw_cards(duel.enemy, OPENING_HAND_SIZE)
-    # Only warm the player's hand: the enemy hand renders face-down (card backs),
-    # so generating its art just starves the art lane and the visible cards.
+    # Warm the player's hand first, then the boss's: the draft is over, so the GPU
+    # is free to illustrate the boss's cards ahead of time — they show art the
+    # moment the boss plays them instead of shimmering in.
     warm_card_art(art_client, duel.player.hand)
+    warm_card_art(art_client, duel.enemy.hand)
     state = replace(
         state,
         enemy_deck=enemy_deck,
@@ -435,8 +437,10 @@ def collect_ready_battle(
 def warm_battle_art(art_client: ArtClient | None, state: RunState) -> None:
     if state.duel is None:
         return
-    # Player hand + the played-card showcase are visible; the enemy hand is not.
+    # Post-draft the GPU is free: warm the player's hand, the boss's hand (so its
+    # plays show art instantly), and the played-card showcase.
     warm_card_art(art_client, state.duel.player.hand)
+    warm_card_art(art_client, state.duel.enemy.hand)
     warm_card_art(art_client, tuple(card for _, card in state.showcase))