Upgrade to pytest 9.2.0 and a supported pytest-asyncio version #2114

Background

The development dependencies currently constrain pytest-asyncio to >=0.21,<0.22. pytest-asyncio 0.21.2 accesses the private pytest attribute FixtureManager._arg2fixturedefs, which was removed in pytest 9.2.0. With that combination, test collection fails with:

AttributeError: FixtureManager object has no attribute _arg2fixturedefs

The latest-dependencies CI job began selecting pytest 9.2.0 when it crossed the repository two-week release cutoff. PR #2113 caps pytest below 9.2 as a temporary workaround.

Proposed work

• Upgrade pytest-asyncio to a supported release compatible with pytest 9.2.0 and the Python versions supported by this repository.
• Migrate the session-scoped event_loop override in tests/conftest.py to the supported loop-scope configuration. pytest-asyncio 1.0 removed the old event_loop fixture mechanism.
• Preserve the loop sharing required by session-scoped async fixtures and verify fixture setup, teardown, and test isolation.
• Remove the temporary pytest<9.2 cap and refresh uv.lock without unrelated dependency churn.
• Account for the two-week dependency cutoff when choosing the plugin release.

Validation

• Test collection succeeds with pytest 9.2.0 and the chosen plugin version.
• The full test suite and latest-dependencies CI job pass, including workflow-environment tests and the supported Python/platform matrix.
• Async resources are cleaned up without new loop-scope, closed-loop, or resource-leak failures.

References

• Temporary compatibility cap: Cap pytest below 9.2 for pytest-asyncio compatibility #2113
• Observed failure: https://github.com/temporalio/sdk-python/actions/runs/42905720512/job/130143059734
• Plugin changelog and migration references: https://pytest-asyncio.readthedocs.io/en/stable/reference/changelog.html

pytest-asyncio 1.4.1.post1 is a candidate: its metadata allows pytest>=8.4 without an upper bound. Compatibility with this repository still needs to be validated.