Codex review round four: workflows execute helper scripts from the
workflow ref, so comparing only the .github/workflows tree missed
script-only harness changes. Harness equivalence now means the git tree
diff between the candidate run's head SHA and the current workflow SHA
is itself release-metadata-only, using the same canonical classifier as
the target delta. The classifier's worktree overlay no longer applies
when --head is an explicit SHA, keeping SHA-exact comparisons exact.
