fix(detector): detect function attribute replay

[prasannakotyal]

Summary

Targets KG red #151, where custom_kernel stores the first output on the function object itself and later returns that saved value from an input-independent fast path.

This adds a narrow FUNCTION_ATTRIBUTE_REPLAY detector. It requires:

• an entrypoint function body using custom_kernel.<attr> or getattr(custom_kernel, "<attr>")
• a call-free early return from that function-attribute state or a local alias to it
• no input parameter reference in the replay guard
• mutation of that same state from input-derived values, including direct assignment or container methods like .append(...)

Plain function metadata, constant flags, and workspace attributes that still compute from the current input stay out of scope.

KernelGuard-Red-Submission: 151

Local verification

• red_31_function_attr_replay -> FUNCTION_ATTRIBUTE_REPLAY, should_filter=True
• red_486_function_attr_list_replay -> FUNCTION_ATTRIBUTE_REPLAY, should_filter=True
• red_487_function_attr_namespace_replay -> FUNCTION_ATTRIBUTE_REPLAY, should_filter=True
• clean_metadata -> stays valid
• clean_attr_constant -> stays valid
• clean_workspace_attr -> stays valid
• python -m py_compile kernelguard.py

[github-actions]

KernelGuard Blue Evaluation

• Evaluation job: 59
• Blue submission: 39
• Result: passed
• Target red submission caught: True
• Validation suite: TP 20/20, FP 20/20
• Surgicalness score: 1.0
• Workflow run: https://github.com/SinatrasC/kernelguard/actions/runs/25237847712

[SinatrasC]

Thanks for the KernelGuard Flywheel Campaign contribution. We are not merging this narrow variant separately because the consolidated rule-family implementation in #273 is the merge path for this detector area.