Worker rotation via the longest-idle criteria

[AlanCoding]

Fixes #156

This doesn't make it configurable, because I see no need to make it configurable. Workers are interchangeable, and this is the only reason we have to have any selection criteria for free workers (postgres connection timeout).

I thought about tracking the last-finished timestamp in the PoolWorker data structure, but then realized that is way more complicated than the obvious solution. So I thought dequeue, but that also gets complicated because there aren't good built-ins for this. On other other hand, OrderedDict is just 💯

Finished a task? Go to the end of the line.

Need a worker to start a task? Look starting from the front of the line.

---

Note

Implements longest-idle worker selection by ordering workers and rotating finished workers to the end, with tests and race-safe handling.

• Worker Pool:
  • Use OrderedDict for WorkerData.workers to preserve order of workers (dispatcherd/service/pool.py).
  • Add WorkerData.move_to_end(worker_id) and call it in process_finished to rotate the finished worker to the end.
  • Handle missing worker in move_to_end gracefully with a warning (race-safe).
  • Update protocol WorkerData to include move_to_end (dispatcherd/protocols.py).
• Imports:
  • Add OrderedDict import in pool.py.
• Tests:
  • Add tests/unit/service/test_worker_order.py verifying workers reorder and dispatch to the longest-idle worker, and that move_to_end logs a warning if the worker was removed.

^{Written by Cursor Bugbot for commit 8b8afec. This will update automatically on new commits. Configure here.}

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud