Initial commit

frontend/src/engine/EventBus.ts

@@ -0,0 +1,11 @@
+import mitt, { type Emitter } from "mitt";
+import type { SyncEventMap } from "@bach-to-basics/shared";
+
+// mitt's generic constraint requires Record<string | symbol, unknown>.
+// We cast our typed map through a compatible intermediate type.
+type BusEvents = SyncEventMap & Record<string | symbol, unknown>;
+
+const bus = mitt<BusEvents>();
+
+export type EventBus = Emitter<BusEvents>;
+export default bus;