Fix cross-thread JSString deinit by wrapping JSObject instead of raw ref #2625

Job	Run time
check-bridgejs-generated	2m 46s
Test BridgeJS against Swift versions (swift:6.3, 603.0.0)	3m 4s
format	1m 3s
Test BridgeJS against Swift versions (swift:6.1.2, 601.0.0)	3m 6s
Test BridgeJS against Swift versions (swift:6.2, 602.0.0)	2m 57s
Build and Test (ubuntu-22.04, https://download.swift.org/swift-6.1-release/ubuntu2204/swift-6.1-R...	14m 1s
Build and Test (ubuntu-24.04, https://download.swift.org/swift-6.3-branch/ubuntu2404/swift-6.3-DE...	12m 33s
build-examples	21m 8s
Build and Test (ubuntu-22.04, https://download.swift.org/development/ubuntu2204/swift-DEVELOPMENT...	18m 43s
prettier	15s
Build for native target (macos-15, Xcode_16.4)	3m 47s
Build and Test (ubuntu-24.04, https://download.swift.org/development/ubuntu2404/swift-DEVELOPMENT...	12m 54s
deploy-examples	0s
	1h 36m 17s

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