docs(dot/sync/worker): add comments for the worker

## Issue summary
Adding comments to the type worker in sync package should help clarify the functionality and design of the code, making it easier to understand and maintain

Start by locating the worker type in the sync package and read its surrounding implementation to understand its responsibilities and design. Add comments that clarify the worker's functionality and design without changing behavior. Consider the issue complete when the worker's purpose and key design decisions are understandable from the code.

Written by the indexing model from the issue text.