Split from #465; parent tracking #66 and #461. A bounded regression holds the terminated JavaScript Worker alive, queues a transferred MessagePort while its worker is blocked in a finite timer callback, then terminates before message delivery. Current Home leaves the surviving peer open (close count 0); Node closes it once. This is separate from GC or native CppTask capture collection: Worker::m_toWorker itself owns the undelivered transfer until Worker destruction.
The implementation checkpoint takes ownership of Worker.cpp via unified webcore-5, preserving all external companion implementations and the byte-identical Worker.h ABI. On stop, seal the incoming inbox under its admission lock, extract queued messages, and destroy them outside Worker/context-map locks. Late posts during Closing must serialize normally but not retain undeliverable transfers. Do not discard accepted parent-bound messages or run cancelled user handlers. Preserve the existing linked pre-enqueue reference-release hook and prevent startup from reopening a closing worker.
Verify retained-wrapper and release/GC variants, late posts, local queued transfers, nested-worker termination, exactly-once close/exit, normal delivery controls, and Node-API/FFI teardown. Generic task cancellation and callback-only poll cleanup remain #465; native work-pool quiescence is #468. Native build/verification in progress; not yet a completion or publication claim.