fix(bench): reject failed processes before scoring output

[DivyamTalwar]

Summary

Fixes #17.

The benchmark path parses its captured speed table without checking subprocess returncode. A failed run can therefore be scored or offered as a contribution. Reject nonzero exits before parsing and scoring; preserve successful results and bound the diagnostic tail.

Testing

Base: 252e5193902d466726da9af75047dfffff2ae662. Debian 12 Linux aarch64 in a nonroot disposable container, Python 3.11. The full existing smoke exits 0 with eight explicitly reported pre-existing optional research/hardware skips. It also prints baseline diagnostic skips where simulator/research dependencies are absent; no skipped check is counted as a pass. No Windows run or GPU/real-model benchmark is claimed.

The same final test files fail against unchanged production; the corrected branch gives:

Focused: 13 passed in 0.05s
Full applicable suite: 8 SKIPPED (a skip is not a pass):
all green

python tests/smoke.py
ruff check quantprobe
ruff format --check quantprobe
# Bandit medium-severity checks on changed package modules
git diff --check

All applicable commands above exited 0 locally. The snapshot is a complete upstream checkout plus this branch's exact changed-file bytes; no test is a copied production-function reimplementation. External I/O is mocked where stated. Dependencies and lockfiles are unchanged.

Security And Data Access

No credential, production-data, authentication, read-only guardrail or privileged workflow changes are included. Tests use synthetic inputs and disposable paths. No new benchmark, fitted law, or hardware capability is claimed.

Notes

This validates exit-status handling with a synthetic process boundary, not a performance benchmark. Existing hardware laws, calibration values and scoring formulas are unchanged.

AI-assisted implementation, isolated same-provider source review, and controller regression checks are disclosed. They are not maintainer approval, cross-vendor certification, or hosted CI. One focused, signed-off commit; no generated logs, personal config, model weights or worktree state is included.

Draft pending upstream CI and maintainer review. Companion changes touching the same module/test hook may require rebasing as they land; no combined branch is being submitted.