fix: cancel losing timeout in AudioMixer race to prevent timer leak

[LautaroPetaccio]

Why

AudioMixer.getContribution() uses Promise.race([iterator.next(), this.timeout(ms)]) to race each stream against a deadline. When the iterator wins (the normal case), the losing timeout's setTimeout is never cleared. It fires harmlessly but creates an orphaned timer on every mixing iteration. Under sustained mixing this creates a steady stream of wasted work, and in pathological cases can pressure the timer heap.

How

Replace the old timeout() method (which returned an uncancellable promise) with timeoutRace(), which returns both the race promise and a clearTimeout handle. After the race resolves in getContribution(), cancel() is called immediately to clear the losing timer.

Test coverage

Three new unit tests in audio_mixer.test.ts:

• completes mixing without lingering timers when iterator is fast — verifies mixing works correctly with a long timeout that always loses the race
• produces frames even with many race iterations — stress test with more frames and iterations
• handles slow streams via timeout path — uses a 1ms timeout with a slow stream to verify the timeout path works and logs the expected warning

[changeset-bot]

🦋 Changeset detected

Latest commit: 54d5d36

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@livekit/rtc-node	Patch

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