Fix dynamic rollout hook module registration

[Newman Gao (bozarnr)]

Summary

• assign each resolved hook path a stable module name and register it in sys.modules before execution
• restore a prior registration if hook execution raises
• add a regression test using a temporary hook file with postponed dataclass annotations, a RolloutCreate transformation, and pickle round-tripping

Validation

• added focused tests/test_hooks.py
• GitHub Actions will run the repository test matrix on this pull request

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