feat(server): per-viewer capture tally on joined and update messages

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/server/src/captures.ts

@@ -0,0 +1,20 @@
+import type { CaptureTally, Color } from '@blind-chess/shared';
+import type { Game } from './state.js';
+
+/**
+ * Per-viewer capture tally derived from move history. `byYou` is the set of
+ * opponent pieces this viewer has captured; `byOpponent` is the set of this
+ * viewer's pieces the opponent has captured. Pure function of move history —
+ * no live board state, no opponent positions.
+ */
+export function captureTally(game: Game, viewer: Color): CaptureTally {
+  const byYou: Record<string, number> = {};
+  const byOpponent: Record<string, number> = {};
+  for (const rec of game.moveHistory) {
+    const captured = rec.capturedPieceType;
+    if (!captured) continue;
+    const bucket = rec.by === viewer ? byYou : byOpponent;
+    bucket[captured] = (bucket[captured] ?? 0) + 1;
+  }
+  return { byYou, byOpponent };
+}

packages/server/src/ws.ts

@@ -19,6 +19,7 @@ import { announce } from './translator.js';
 import { buildView } from './view.js';
 import { consumeCommitToken } from './ratelimit.js';
 import { endGame, finalizeIfEnded } from './game-end.js';
+import { captureTally } from './captures.js';
 
 async function pokeBot(game: Game): Promise<void> {
   const driver = getBotDriver(game.id);
@@ -147,6 +148,7 @@ async function onHello(ctx: SocketCtx, msg: Extract<ClientMessage, { type: 'hell
     mode: game.mode,
     highlightingEnabled: game.highlightingEnabled,
     opponentConnected: !!game.players[color === 'w' ? 'b' : 'w']?.socket,
+    captures: captureTally(game, color),
     aiOpponent: game.aiOpponent,
   });
 
@@ -284,6 +286,7 @@ function sendUpdateTo(
     drawOffer,
     endReason: game.endReason,
     winner: game.winner ?? null,
+    captures: captureTally(game, color),
     aiOpponent: game.aiOpponent,
   });
 }