fix: deduplicate getSid() listeners to prevent leak on concurrent calls

[LautaroPetaccio]

Why

Each getSid() call creates its own RoomSidChanged + Disconnected listener pair. If multiple calls race, only one resolves the SID and cleans up its RoomSidChanged listener — the rest stay attached. Additionally, the Disconnected listener registered via once() was never removed on the success path, persisting until a disconnect event or removeAllListeners().

How

Add a private sidPromise?: Promise<string> field. On the first getSid() call that needs to wait, create the promise and store it. Subsequent concurrent calls return the same promise. When the promise resolves or rejects, sidPromise is cleared so future calls after a reconnect work normally. Both the resolve and reject paths now clean up both listeners — on success, handleDisconnect is removed; on disconnect, handleRoomUpdate is removed.

Test coverage

New E2E test concurrent getSid() calls share a single listener and resolve consistently — fires 3 concurrent getSid() calls, asserts all return the same SID.

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🦋 Changeset detected

Latest commit: 9e38994

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

This PR includes changesets to release 1 package

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@livekit/rtc-node	Patch

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[lukasIO]

This should already be accounted for if you don't remove the handleDisconnect once listener above?

[LautaroPetaccio]

The once-listener depends on the 'disconnected' FFI event arriving and being processed before the 'disconnect' callback resolves. Since we can't guarantee that ordering, and if the callback resolves first, removeAllListeners() wipes the once-listener before it fires, the explicit cleanup here is needed as a safety measure to prevent a stale sidPromise across reconnects.