fix(splash): reuse latest chat message preview

src/lib/chat/splash_latest_message_cache.ts

@@ -0,0 +1,19 @@
+export interface SplashLatestMessageCacheEntry {
+  message: string | null;
+}
+
+export interface SplashLatestMessageCache {
+  clear(): void;
+  get(identity: string): SplashLatestMessageCacheEntry | undefined;
+  set(identity: string, message: string | null): void;
+}
+
+export function createSplashLatestMessageCache(): SplashLatestMessageCache {
+  const entries = new Map<string, SplashLatestMessageCacheEntry>();
+
+  return {
+    clear: () => entries.clear(),
+    get: (identity) => entries.get(identity),
+    set: (identity, message) => entries.set(identity, { message }),
+  };
+}