Trik: posledna karta sa prida bez blikania, kopka sa zmetie k vitazovi

Doteraz sa pri hodeni 4. karty cela kopka na frame stratila (displayedStash
padol na lingeredStash nastaveny az v useEffekte) a nasledne sa vsetky karty
znovu vlietli. Teraz sa previous_stash cita synchronne, takze posledna karta
len pribudne k trom uz leziacim, a potom sa cela kopka odsunie animaciou
smerom k sedadlu, ktore kopku vyhralo (stashWinner podla pravidiel enginu).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/gameRules.ts

@@ -1,4 +1,4 @@
-import type { CardColor, Hand } from '../types';
+import type { CardColor, CardValue, Hand, StashData } from '../types';
 
 export function computePlayable(hand: Hand, ledColor: CardColor | null): Set<string> {
   const keys = Object.keys(hand);
@@ -13,6 +13,35 @@ export function computePlayable(hand: Hand, ledColor: CardColor | null): Set<str
   return new Set(keys);
 }
 
+const VALUE_ORDER: CardValue[] = ['C7', 'C8', 'C9', 'C10', 'LOWER', 'UPPER', 'KING', 'ACE'];
+
+/** Seat that wins a completed 4-card trick — mirrors Stash.get_winner in the
+ *  engine: HEARTS (červeň) is the permanent trump, otherwise the highest card
+ *  of the led colour wins. Safe to call on a partial stash (returns the current
+ *  leader among the cards played so far). */
+export function stashWinner(stash: StashData): number {
+  const led = stash.cards[String(stash.first_player)];
+  if (!led) return stash.first_player;
+  let winner = stash.first_player;
+  let best = led;
+  for (let i = 0; i < 4; i++) {
+    const c = stash.cards[String(i)];
+    if (!c) continue;
+    if (c.color === led.color || c.color === 'HEARTS') {
+      if (c.color === best.color) {
+        if (VALUE_ORDER.indexOf(c.value) >= VALUE_ORDER.indexOf(best.value)) {
+          best = c;
+          winner = i;
+        }
+      } else if (c.color === 'HEARTS') {
+        best = c;
+        winner = i;
+      }
+    }
+  }
+  return winner;
+}
+
 /** The bid the last guesser may not make: the four bids must not sum to the
  *  number of tricks in the round (mirrors Round.add_player_guess in the engine).
  *  Returns null while earlier players are still guessing. */