refactor: remove use of PThread.runningWorkers

[toyobayashi]

emscripten-core/emscripten#26998

[Copilot]

Pull request overview

Removes the now-redundant PThread.runningWorkers array (deprecated upstream in emscripten-core/emscripten#26998) and derives running workers from PThread.pthreads instead. Also tightens the cleanup guard in WASIThreads spawn error handling.

Changes:

• Delete runningWorkers field from ThreadManager and all push/splice maintenance sites.
• Replace runningWorkers.forEach usages with Object.values(PThread.pthreads).forEach in TSFN, async-work, and the associated @__postset comment.
• Consolidate cleanThread calls in WASIThreads spawn into a single catch block guarded by worker !== undefined && tid !== undefined.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/wasi-threads/src/thread-manager.ts	Remove runningWorkers field/maintenance; iterate pthreads in terminateAllThreads.
packages/wasi-threads/src/wasi-threads.ts	Make tid optional and move cleanup into the catch block with guards.
packages/emnapi/src/threadsafe-function.ts	Replace runningWorkers.forEach with Object.values(PThread.pthreads).forEach.
packages/emnapi/src/core/async-work.ts	Same replacement for the async-work listener setup.
packages/emnapi/src/emscripten/async.ts	Update @__postset doc comment to reflect the new iteration.

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