fix(detector): detect lambda setitem replay

[prasannakotyal]

KernelGuard-Red-Submission: 133

Detects lambda entrypoints that replay from captured state after mutating it with __setitem__.

The pass requires:

• module-level custom_kernel = lambda ...
• conditional expression fast path that does not depend on live input
• fast-path return by subscript from captured state
• fallback branch that mutates the same captured state via __setitem__ and returns it

Local validation:

• uv run python -m py_compile kernelguard.py
• uv run python /home/nino/repos/paradigma/kernelguard_bypasses/eval_blue_patch.py /home/nino/repos/paradigma/competition_state/kernelguard_mirror/kernelguard.py

Target red fixture: red_12_lambda_dict_setitem_replay.py

[github-actions]

KernelGuard Blue Evaluation

• Evaluation job: 146
• Blue submission: 118
• 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/25254446382

[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.