Event names are strings, but repeated strings become difficult to maintain as an event bus grows. A static getter gives a class-level constant-like name that callers can reuse without creating an instance. section 14.6
Centralizing an event type
Define the event name once: `static get PLAYLIST_UPDATE_EVENT() { return 'onPlaylistTimeUpdate'; }`. Dispatch with `new CustomEvent(WorkoutPlanData.PLAYLIST_UPDATE_EVENT, { ... })`, and listen with `EventBus.addEventListener(WorkoutPlanData.PLAYLIST_UPDATE_EVENT, callback)`. The getter is accessed through `WorkoutPlanData`, not through a created workout-plan object.
