refactor: remove CommonJS worker and thread management files

- Deleted `threadman_thread.cjs` and `threadman_worker.cjs` as part of the transition to ESM.
- Updated `threadman.node.js` to use a build-time injected worker path instead of relying on `__dirname`.
- Modified `vite.config.js` to inject `__BUILD_WORKER_PATH__` during the build process, ensuring correct worker path resolution.

Author: Kolezhniuk