Interface WebWorkerHostOptions

Name of the non-standard event this runtime emits when a worker's thread ends. Bun emits 'close'; Deno emits nothing at all, so it passes nothing and the handles this host produces omit onExit entirely.

Omitted rather than registered-and-silent on purpose: a present onExit that can never fire would let a consumer conclude it has worker-death detection while a dead worker still went unnoticed.