Stabilize tq signal-handling tests

[steve-the-edwards]

Summary

• stabilize the tq signal-handling tests with a shared polling helper that uses bounded linear backoff
• wait for a running queue row to also record child_pid before asserting on subprocess cleanup
• poll waiter process exit after SIGINT with the same timeout budget instead of assuming teardown finishes on a single fixed wait tick

Why

• main failed after merging PR Add hierarchical queue capacities #29 in CI run 24741062035
• first failing job: test (3.12) / 72380570655
• raw failure: tests/test_tq_cli.py::TestSignalHandling::test_multiple_waiters_cancelled
• related sibling failure also showed up in run 24741092691: tests/test_tq_cli.py::TestSignalHandling::test_sigint_cleanup_running_task

Testing

• python -m py_compile tests/test_tq_cli.py
• uv run ruff check tests/test_tq_cli.py
• uv run pytest -v tests/test_tq_cli.py

Review

• reran amp review "origin/main...HEAD" after the bounded-backoff refactor
• the tool returned the updated diff summary, then failed with an upstream 429 rate limit before producing any findings

[steve-the-edwards]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. 👍

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".