[xunyoyo]

Summary

• add license header, shared helpers, and docstrings to ResourceManagerV1 tests while cleaning imports
• expand ResourceManagerV1 test suite to cover multimodal boundary handling, preemption edge cases, and prefix cache errors
• ensure stubs and monkeypatching reflect project expectations for style and xpu gating

Testing

• pytest -c tests/cov_pytest.ini tests/engine/test_resource_manager_v1.py -vv
• pytest -c tests/cov_pytest.ini --cov=fastdeploy.engine.sched.resource_manager_v1 --cov-report=term-missing tests/engine/test_resource_manager_v1.py -vv
• pre-commit run --files fastdeploy/engine/sched/resource_manager_v1.py tests/engine/test_resource_manager_v1.py

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Codex Task