Verify comment-only refactors by diffing stripped code

When agents rewrite comments across a large C/Python codebase, prove nothing else changed. Commit the code first. Then, for C, compare gcc -fpreprocessed -dD -E -P -x c - output of HEAD vs working copy with whitespace collapsed: it strips comments without expanding macros or includes. For Python, compare ast.dump after dropping docstrings. Gotcha: a module docstring used as argparse description=__doc__ is user-visible help text, so treat it as code. Also: CI that pins every grading container to the same --cpuset-cpus while running jobs in parallel makes timing-based scores depend on co-scheduled jobs.