Add cumulative PnL tracking to Blackjack game

- Added cumulativePnl field to PlayerSeat and PlayerSeatView types
- Added myCumulativePnl to PlayerView for UI display
- Track net profit/loss across rounds in the game state
- Update round result banner to show both round net and total balance
- Add player seat PnL indicator with color coding (green/red)
- Preserve cumulativePnl when players stay seated through rounds
- Initialize new players with cumulativePnl = 0
- Added comprehensive tests for cumulative PnL tracking

panel/src/games/blackjack/BlackjackGame.tsx

@@ -23,6 +23,8 @@ interface PlayerSeatView {
     hands: PlayerHandView[];
     activeHandIndex: number;
     hasBet: boolean;
+    /** Cumulative PnL from all previous rounds. */
+    cumulativePnl: number;
 }
 
 interface BlackjackViewBase {
@@ -42,6 +44,8 @@ interface PlayerView extends BlackjackViewBase {
     canAct: boolean;
     canSplit: boolean;
     canDoubleDown: boolean;
+    /** Cumulative PnL for the current player. */
+    myCumulativePnl: number;
 }
 
 function isPlayerView(state: unknown): state is PlayerView {
@@ -207,6 +211,16 @@ function Seat({ seat, playerName, isMe, isActivePlayer, activeHandIdx, betAmount
     const hasHands = seat.hands.length > 0;
     const compact = seat.hands.length > 2;
 
+    // Calculate current round PnL for the display
+    const currentRoundPnl = seat.hands.reduce((sum, h) => {
+        if (!h.result) return sum; // Not yet resolved
+        const handWin = h.bet * betAmount;
+        if (h.result === "win" || h.result === "blackjack") return sum + handWin;
+        if (h.result === "push") return sum; // Push returns bet
+        return sum - handWin; // Lose
+    }, 0);
+    const totalPnl = seat.cumulativePnl + currentRoundPnl;
+
     return (
         <div className={`flex flex-col items-center gap-1.5 transition-all ${
             isActivePlayer ? "scale-105" : ""
@@ -256,6 +270,21 @@ function Seat({ seat, playerName, isMe, isActivePlayer, activeHandIdx, betAmount
             {hasHands && betAmount > 0 && (
                 <BetChip bet={seat.hands.reduce((sum, h) => sum + h.bet, 0)} betAmount={betAmount} />
             )}
+
+            {/* Cumulative PnL indicator */}
+            {(seat.cumulativePnl !== 0 || hasHands) && (
+                <div className={`flex items-center gap-1 text-xs font-bold rounded px-2 py-0.5 ${
+                    totalPnl > 0
+                        ? "bg-emerald-500/20 text-emerald-400"
+                        : totalPnl < 0
+                            ? "bg-red-500/20 text-red-400"
+                            : "bg-blue-500/20 text-blue-300"
+                }`}>
+                    {totalPnl > 0 && <ChevronsUp className="w-3.5 h-3.5" />}
+                    {totalPnl < 0 && <ChevronsUp className="w-3.5 h-3.5 rotate-180" />}
+                    <span>{totalPnl > 0 ? "+" : ""}{totalPnl} AU</span>
+                </div>
+            )}
         </div>
     );
 }
@@ -318,24 +347,37 @@ function DealerArea({ dealerHand, visibleValue, fullValue }: {
 
 // ── Round result banner ──
 
-function RoundResultBanner({ roundNumber, roundResult, myPlayerId, betAmount }: {
+function RoundResultBanner({ roundNumber, roundResult, myPlayerId, betAmount, myCumulativePnl }: {
     roundNumber: number;
     roundResult: GameUIProps["roundResult"];
     myPlayerId: string;
     betAmount: number;
+    myCumulativePnl: number;
 }) {
-    const myPayout = roundResult?.payouts[myPlayerId];
+    const myPayout = roundResult?.payouts?.[myPlayerId];
+    // Calculate this round's net result
+    const roundNet = myPayout?.net ?? 0;
+    // Current balance after this round (includes round result + cumulative from before)
+    const currentBalance = myCumulativePnl;
 
     return (
         <div className="flex items-center justify-center gap-3 bg-black/30 rounded-xl px-4 py-2">
             <span className="text-xs text-white/50">Round {roundNumber}</span>
-            {myPayout && betAmount > 0 && (
-                <span className={`text-xs font-semibold ${
-                    myPayout.net > betAmount ? "text-emerald-400" : myPayout.net === betAmount ? "text-blue-400" : "text-white/60"
+            <div className="flex items-center gap-2">
+                {myPayout && betAmount > 0 && (
+                    <span className={`text-xs font-semibold ${
+                        myPayout.net > betAmount ? "text-emerald-400" : myPayout.net === betAmount ? "text-blue-400" : "text-white/60"
+                    }`}>
+                        Round: {myPayout.net > 0 ? "+" : ""}{myPayout.net} AU
+                    </span>
+                )}
+                <div className="w-px h-4 bg-white/20" />
+                <span className={`text-xs font-bold ${
+                    currentBalance > 0 ? "text-emerald-400" : currentBalance < 0 ? "text-red-400" : "text-blue-300"
                 }`}>
-                    +{myPayout.net} AU
+                    Total: {currentBalance > 0 ? "+" : ""}{currentBalance} AU
                 </span>
-            )}
+            </div>
         </div>
     );
 }
@@ -358,6 +400,15 @@ export function BlackjackGame({ state, myPlayerId, isSpectator, onAction, player
     const mySeat = view.seats[myPlayerId];
     const myBetPlaced = mySeat?.hasBet ?? false;
 
+    // Calculate current balance (if betting) or just track profit/loss
+    const balance = betAmount > 0 && mySeat?.hands.length === 0
+        ? 0 // Not yet bet for this round
+        : mySeat?.hands.reduce((sum, h) => sum + (h.result === "win" || h.result === "blackjack"
+            ? h.bet * betAmount
+            : h.result === "push" ? h.bet * betAmount
+            : 0), 0) - (myBetPlaced ? mySeat.hands.reduce((sum, h) => sum + h.bet * betAmount, 0) : 0);
+    const myPnl = (mySeat?.cumulativePnl ?? 0) + balance;
+
     // Determine who can sit (spectators during betting phase)
     const canSitDown = isSpectator && isBetting && view.turnOrder.length < 6;
 
@@ -529,6 +580,7 @@ export function BlackjackGame({ state, myPlayerId, isSpectator, onAction, player
                     roundResult={roundResult}
                     myPlayerId={myPlayerId}
                     betAmount={betAmount}
+                    myCumulativePnl={(view as PlayerView)?.myCumulativePnl ?? 0}
                 />
             )}