Queue Improvements

[ronfriedhaber]

• Persevere caller's options, results in safer implementation memory-reference wise
• Notify status change solely when status (state) differs
• Support cancel token for async termination

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Note

Low Risk
Localized queue client behavior changes with tests; cancellation is opt-in and does not alter default submit/poll semantics.

Overview
submit_and_poll now copies the caller’s options dict before popping on_status_change, so the original mapping is not mutated in place.

Polling can be stopped cooperatively via an optional cancel_token (asyncio.Event). A new _wait_or_cancel helper replaces fixed asyncio.sleep during the initial delay and between status checks; if the token is set, polling raises asyncio.CancelledError (including before submit when the token is already set).

on_status_change is invoked only when the job status string actually changes, while still firing once for the initial post-submit status.

Tests tighten the status-callback sequence expectations, assert the caller’s options dict is preserved, and add coverage for cancellation before submit.

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