perf(renderer): cache stable team message keys

src/renderer/utils/teamMessageKey.ts

@@ -2,13 +2,45 @@ import type { InboxMessage } from '@shared/types';
 
 const FALLBACK_SLICE = 80;
 
+interface CachedMessageKey {
+  readonly messageId: InboxMessage['messageId'];
+  readonly timestamp: InboxMessage['timestamp'];
+  readonly from: InboxMessage['from'];
+  readonly text: InboxMessage['text'];
+  readonly key: string;
+}
+
+const messageKeyCache = new WeakMap<InboxMessage, CachedMessageKey>();
+
 /**
  * Stable key for a team message. Prefer messageId; otherwise build from timestamp, from, and text.
  */
 export function toMessageKey(message: InboxMessage): string {
-  if (typeof message.messageId === 'string' && message.messageId.trim().length > 0) {
-    return message.messageId;
+  const cached = messageKeyCache.get(message);
+  if (
+    cached &&
+    cached.messageId === message.messageId &&
+    cached.timestamp === message.timestamp &&
+    cached.from === message.from &&
+    cached.text === message.text
+  ) {
+    return cached.key;
   }
-  const text = (message.text ?? '').slice(0, FALLBACK_SLICE);
-  return `${message.timestamp}-${message.from}-${text}`;
+
+  const rawMessageId = typeof message.messageId === 'string' ? message.messageId : '';
+  const trimmedMessageId = rawMessageId.trim();
+  const key =
+    trimmedMessageId.length > 0
+      ? rawMessageId
+      : `${message.timestamp}-${message.from}-${(message.text ?? '').slice(0, FALLBACK_SLICE)}`;
+
+  messageKeyCache.set(message, {
+    messageId: message.messageId,
+    timestamp: message.timestamp,
+    from: message.from,
+    text: message.text,
+    key,
+  });
+
+  return key;
 }