fix(ext/node): ensure 'exit' event is fired only once for worker_threads

[TarikSogukpinar]

fix(node:worker_threads): ensure 'exit' event fires once and matches Node.js behavior

related issue:
closes #30013

The 'exit' event in node:worker_threads was not consistently fired, or in some cases emitted multiple times, diverging from Node.js behavior.

How

• Added a private #exited flag to prevent duplicate 'exit' emissions
• Emit 'exit' with code 1 on TerminalError and with code 0 on Close
• Removed direct 'exit' emission from terminate() — event is now triggered by host signals
• Verified with both success and failure worker scenarios to ensure parity with Node.js and Bun

[CLAassistant]

All committers have signed the CLA.

[Copilot]

Pull Request Overview

This PR refactors the worker exit event handling to emit the 'exit' event based on control messages received from the worker, rather than immediately when terminate() is called. The change introduces a guard flag to ensure the exit event is only emitted once.

Key changes:

• Added #exited flag to track whether the exit event has been emitted
• Moved exit event emission from terminate() method to control message handlers (TerminalError and Close cases)
• Exit event now emits with exit code 1 for TerminalError and 0 for normal Close

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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[bartlomieju]

Thanks for the PR, are there tests you could add?

[TarikSogukpinar]

Thanks for the PR, are there tests you could add?

I will check the tests and add them as soon as possible.

[TarikSogukpinar]

Thanks for the PR, are there tests you could add?

Tests have been added and verified locally — all passing

[bartlomieju]

Great fix, thanks!