KTLO pypy3.10: finaliser backstop test fails on main #2481

Python pypy3.10 (KTLO) fails one test on main and the leg is only green because KTLO is non-blocking.

• Run 41149347371, head 4ca3f30d7, job 124382682020.
• Failing id: tests/foundation/test_extraction_ownership.py::FinaliserBackstopWithoutDel::test_finaliser_alone_releases_an_abandoned_handle.
• Assertion: 1 != 0 : without __del__ the handle outlived the extractor.
• Other pypy3.10 jobs and the Integration leg pass. The Integration Python pypy3.10 (KTLO) annotation "Could not compute the fixture-tier selection" needs a separate look.

Not root-caused. Likely a pypy GC-timing assumption (no refcounting, so collect_until may not reach the finaliser within its grace), but unverified. Next step: reproduce on pypy3.10, then decide between a longer grace and an explicit gc loop.