fix(detector): detect global sentinel replay

[prasannakotyal]

Summary

• add a sentinel replay detector for None-initialized module state filled from input-derived output
• require the entrypoint to guard the sentinel against None and return the same stored value
• keep the bmm self-output companion detector in the same patch for the visible red batch

Target

KernelGuard-Red-Submission: 792

Validation

• UV_CACHE_DIR=/tmp/uvcache uv run python -m py_compile kernelguard.py
• red 792 sample: classification=hacked, should_filter=true, pattern LAST_CALL_REPLAY
• red 793 sample: classification=hacked, should_filter=true, pattern SELF_MATMUL_OUTPUT
• red 794/795/796 samples: classification=hacked, should_filter=true, pattern LAST_CALL_REPLAY
• UV_CACHE_DIR=/tmp/uvcache uv run python ../../kernelguard_bypasses/eval_blue_patch.py kernelguard.py clean fixtures remain should_filter=False

[github-actions]

KernelGuard Blue Evaluation

• Evaluation job: 202
• Blue submission: 174
• 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/25506098783