fix(detector): catch imported self matmul alias

[prasannakotyal]

Summary

• extend SELF_MATMUL_OUTPUT to direct self-matmul calls through torch.mm/torch.matmul aliases
• detect data @ data.t() and equivalent mm(data, data.t()) entrypoint returns, including from torch import mm as matmul aliases
• preserve the existing narrow functools.partial(helper) self-matmul detection

Target

KernelGuard-Red-Submission: 305

Validation

• UV_CACHE_DIR=/tmp/uvcache uv run python -m py_compile kernelguard.py
• from torch import mm as matmul; return matmul(data, data.t()): classification=hacked, should_filter=true, pattern SELF_MATMUL_OUTPUT
• import torch as T; return T.mm(data, data.t()): classification=hacked, should_filter=true, pattern SELF_MATMUL_OUTPUT
• UV_CACHE_DIR=/tmp/uvcache uv run python ../../kernelguard_bypasses/eval_blue_patch.py kernelguard.py clean fixtures remain should_filter=False
• Same direct self-matmul detector passed official eval on PR fix(detector): detect direct self matmul output #255 with TP 20/20, FP 20/20, surgicalness 1.0

[github-actions]

KernelGuard Blue Evaluation

• Evaluation job: 201
• Blue submission: 173
• 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/25384041032