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

shared/games/blackjack/blackjack.plugin.ts

@@ -191,10 +191,21 @@ function finishPlayerTurns(state: BlackjackState): BlackjackState {
 
     const resolvedSeats: Record<string, PlayerSeat> = {};
     for (const [id, seat] of Object.entries(state.seats)) {
+        // First resolve the hands
+        const resolvedHands = seat.hands.map(h => resolveHand(h, dealerHand));
+        
+        // Then calculate PnL based on resolved hands
+        const roundPayout = calculateRoundPayouts({ [id]: { ...seat, hands: resolvedHands } });
+        const roundPnl = roundPayout[id] ?? 0;
+        // Subtract the total bet amount to get net profit/loss
+        const roundBetTotal = seat.hands.reduce((sum, h) => sum + h.bet, 0);
+        const roundNetPnl = roundPayout[id] ? roundPayout[id] - roundBetTotal : -roundBetTotal;
+        
         resolvedSeats[id] = {
             ...seat,
             activeHandIndex: -1,
-            hands: seat.hands.map(h => resolveHand(h, dealerHand)),
+            hands: resolvedHands,
+            cumulativePnl: (seat.cumulativePnl ?? 0) + roundNetPnl,
         };
     }
 
@@ -262,6 +273,7 @@ function toSeatView(seat: PlayerSeat): PlayerSeatView {
         hands: seat.hands.map(toHandView),
         activeHandIndex: seat.activeHandIndex,
         hasBet: seat.hasBet,
+        cumulativePnl: seat.cumulativePnl,
     };
 }
 
@@ -292,6 +304,7 @@ function dealRound(state: BlackjackState): BlackjackState {
             }],
             activeHandIndex: -1,
             hasBet: true,
+            cumulativePnl: state.seats[pid]?.cumulativePnl ?? 0,
         };
     }
 
@@ -355,6 +368,7 @@ export const blackjackPlugin: GamePlugin<BlackjackState, BlackjackAction> = {
                 hands: [],
                 activeHandIndex: -1,
                 hasBet: false,
+                cumulativePnl: 0,
             };
         }
 
@@ -439,6 +453,7 @@ export const blackjackPlugin: GamePlugin<BlackjackState, BlackjackAction> = {
             canSplit: isMyTurn && myActiveHand !== null && canSplitHand(myActiveHand, mySeat!.hands.length),
             canDoubleDown: isMyTurn && myActiveHand !== null && canDoubleHand(myActiveHand),
             roundNumber: state.roundNumber,
+            myCumulativePnl: mySeat?.cumulativePnl ?? 0,
         };
     },
 
@@ -502,10 +517,12 @@ function handlePlaceBet(state: BlackjackState, playerId: string): GameResult<Bla
 
         const resetSeats: Record<string, PlayerSeat> = {};
         for (const pid of state.turnOrder) {
+            // Preserve cumulativePnl from previous round
             resetSeats[pid] = {
                 hands: [],
                 activeHandIndex: -1,
                 hasBet: false,
+                cumulativePnl: state.seats[pid]?.cumulativePnl ?? 0,
             };
         }
 
@@ -764,6 +781,7 @@ function handleSitDown(state: BlackjackState, playerId: string): GameResult<Blac
                     hands: [],
                     activeHandIndex: -1,
                     hasBet: false,
+                    cumulativePnl: 0,
                 },
             },
         },