workflow-fix: verify_plan check — re-extracted reference arms never silently replace a committed headline

Overview / Motivation

Auto-filed by the workflow-fix-on-bug protocol from a Codex critic note raised on task #811 (emitting agent: codex-critic Statistics lens, surfaced by the orchestrator).

Goal

Add a verify_plan.py check: a follow-up plan that RE-EXTRACTS prior-headline reference arms AND folds into an existing clean-result must explicitly distinguish "same-pass comparator" values from "prior committed headline" values (a reference flip is replication-stability evidence, never a silent headline replacement).

Workflow gap

• Bug observed: #811 plan v3 §6 said "adjudication then uses THIS round's internally consistent store", which would let a regenerated-R flip in a re-extracted reference silently move the already-adjudicated clean-result headline for reasons unrelated to the round's new arms.
• Why it is a workflow gap: follow-up rounds that re-extract reference arms + fold into an existing clean-result are a recurring plan shape (#811 rounds 1-2 both did); no mechanical check enforces the committed-cells-remain-evidence rule.
• Confidence (emitter): medium

Proposed change (candidate diff sketch — refine in planning)

• In scripts/verify_plan.py: parse plan text for a parity/reference clause; if the plan
• both re-extracts prior headline references AND folds into an existing clean-result
• (followup-scope marker present + reference arms named), require an explicit sentence
• distinguishing same-pass comparator values from prior committed headline values;
• WARN (not FAIL) when absent.

Scope / surfaces

• Primary target: scripts/verify_plan.py
• Grep the workflow surface for related parity-clause conventions before editing; list hits in the plan.

Constraints / invariants

• Workflow-surface only — never experiment code, configs/, or tasks/.
• scripts/workflow_lint.py --check-asks passes; ruff on touched files passes.
• This session runs under EPM_WORKFLOW_FIX_SESSION=1 and carries a workflow_fix_target: Provenance line — it MUST NOT auto-route any of its own subagents' workflow-fix candidates (recursion guard).

Provenance

• workflow_fix_target: scripts/verify_plan.py
• fingerprint: (computed at filing)

Codex Statistics critic note (task #811 plan v3, 2026-07-03): "This is a recurring workflow-surface verifier candidate for follow-up plans that re-extract reference arms and fold into an existing clean-result. ... Check sketch: parse plan text for a parity/reference clause; if it both re-extracts prior headline references and folds into an existing clean-result, require an explicit sentence distinguishing 'same-pass comparator' values from 'prior committed headline' values."