Fix record_thread overwriting active worker IDs

[MoneroOcean]

Motivation

• The record_thread helper reset worker_ids before adding a single thread_id, which caused previously created workers to be dropped from messageWorkers broadcasts and lose future control messages.

Description

• Change record_thread in index.js to append the thread_id only if not already present (i.e. if (!worker_ids.includes(thread_id)) worker_ids.push(thread_id);), preserving existing tracked worker IDs and avoiding duplicates while keeping create_thread behavior unchanged.

Testing

• Ran npm test; the automated test run could not complete because npm failed to fetch the nan dependency (403 Forbidden), so the native addon build and test suite did not run successfully.

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Codex Task