Support iterable inputs in LifecycleTransition

[Old-Ding]

Summary

• materialize LifecycleTransition iterable inputs once before validation
• support generators and iterators as promised by the public Iterable annotations
• keep the existing empty-input ValueError behavior for iterator inputs

Testing

• focused source behavior probe: baseline raises TypeError for iterators, while the fixed constructor accepts them
• verified empty iterators still raise the existing field-specific ValueError
• python -m py_compile for both modified Python files
• flake8 on both modified files with the repository's existing E501/W504 exclusions
• git diff --check

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