tuning: fix thread counts #2648

Job	Run time
Evaluation-based tests	19m 55s
Minimal dependency tests	15m 45s
Minimal dependency tests (all options)	17m 53s
Rust test coverage	13m 44s
Demos, examples, and docs	4m 26s
Vanilla Python 3.13 on ubuntu-24.04-arm	13m 24s
Vanilla Python 3.12.5 on ubuntu-24.04-arm	16m 2s
Vanilla Python 3.14t on ubuntu-latest	11m 26s
Vanilla Python 3.13 on macos-latest	16m 55s
Vanilla Python 3.13 on ubuntu-latest	13m 40s
Vanilla Python 3.12.5 on macos-latest	16m 54s
Vanilla Python 3.14t on macos-latest	14m 0s
Vanilla Python 3.12.5 on ubuntu-latest	15m 13s
Vanilla Python 3.14t on ubuntu-24.04-arm	11m 16s
Vanilla Python 3.14 on macos-latest	15m 4s
Vanilla Python 3.12.5 on windows-latest	19m 8s
Vanilla Python 3.14t on windows-latest	15m 10s
Vanilla Python 3.14 on ubuntu-latest	10m 49s
Vanilla Python 3.13 on windows-latest	15m 22s
Vanilla Python 3.14 on ubuntu-24.04-arm	11m 0s
Vanilla Python 3.14 on windows-latest	14m 50s
Test suite results	28s
	5h 2m 24s

Provide feedback