Mock-Masked Stub Trap

The trap

An implementer returns a track/PR with all gates green (pytest passing, mypy/lint clean) — and a load-bearing branch is stubbed in production but appears tested because the test patches the very function that is the stub. The green is hollow: the production code path it claims to cover never runs in any test.

Canonical shape:

# production
def _find_incomplete_run(skill_id):
    return None            # <-- stub; docstring may even admit it