[wieslawsoltes]

An active transferred MessagePort in a dedicated Worker could lose its wrapper during GC because local peer edges end at the isolate boundary. A Worker that installed onmessage or an EventTarget listener could therefore stop receiving future messages after the parent requested low-memory collection.

This change roots only started, remotely entangled ports with active message/messageerror listeners. It releases that root on handler/listener removal, abort/once dispatch, transfer, explicit or collected peer close, Worker termination, navigation, and runtime teardown. Parent low-memory notification now synchronously requests collection on live Worker isolate threads, which makes the cross-isolate regression deterministic.

Validation:

• Chrome 153 contract: 1/1 document, 3/3 subtests; 100 transfer/release cycles in 124 ms
• native contract: 1/1 document, 3/3 subtests; final exact-head run in 852 ms
• native forced-GC lifecycle: 100 cycles in 1.03 s; 2 binding slots, 0 retained bindings, 0 queued messages/bytes; heap 879,384 -> 662,368 bytes; RSS 38.0 -> 41.2 MB
• existing 1,000-cycle same-realm forced-GC stress: p95 2.81 ms, max 11.79 ms; 0 retained/queued; bounded heap/RSS
• existing 10,000-message Worker throughput and complete Worker/MessagePort aggregate pass

Advances #288. Related to #81 and #227.