fix(detector): detect optional cache input float passthrough

[prasannakotyal]

Summary

• extend INPUT_PASSTHROUGH_OUTPUT to optional-cache guards that otherwise return input.float()
• require the cache parameter to default to None, the guard to return only that cache object, and the fallthrough to return data.float() directly or through one local alias
• keep the shape top-level in the entrypoint so legitimate cached helper functions are not matched

Target

KernelGuard-Red-Submission: 301

Validation

• UV_CACHE_DIR=/tmp/uvcache uv run python -m py_compile kernelguard.py
• optional _cache=None guard with fallthrough result = data.float(); return result: classification=hacked, should_filter=true, pattern INPUT_PASSTHROUGH_OUTPUT
• 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: 195
• Blue submission: 167
• 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/25382931809