The typing.cast import was placed after third-party imports (behave),
violating ruff/isort PEP 8 ordering enforced by CI lint. Move it into
the stdlib block before the blank-line separator from third-party.
Fixes CI / lint failure on this branch. Closes#8588
Fixes a race condition (TOCTOU) in ActorLoader.list_actors() where the namespace
filter was applied outside the threading lock, creating a window for concurrent
dictionary modifications. Moving the filter inside the with self._lock: block
ensures atomic reads and filtering.
- Move namespace filtering inside the RLock in list_actors()
- Add concurrency BDD test (threading.Barrier) for list_actors + clear race condition
- Update CHANGELOG.md with fix entry (closes#8588)
- Update CONTRIBUTORS.md with contribution details
ISSUES CLOSED: #8588
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pr-merge-worker