workflow-fix: verifier WARN on stale concern-deferred markers naming addressed concerns

Overview / Motivation

Auto-filed by the workflow-fix-on-bug protocol from a mechanizable finding raised on task #833 (emitting agents: clean-result-critic epm:clean-result-critique v3 + codex-clean-result-critic epm:clean-result-critique-codex v3, agreed procedural item).

Goal

Add a verifier WARN when a <!-- concern-deferred: <id> --> body marker names a concern whose latest concerns.jsonl event is addressed.

Workflow gap

• Bug observed: #833's body carried three stale <!-- concern-deferred: ... --> HTML markers after all three named concerns had transitioned to addressed — the markers misdescribed the resolution (deferred vs addressed) and nothing mechanical flagged them; both LM critics had to catch it as a procedural item.
• Why it is a workflow gap: the concerns-audit check (check 14 family) validates acknowledgment of OPEN concerns but is silent on markers that outlive their concern's resolution, so every fixed-concern round leaves stale markers behind by default.
• Confidence (emitter): medium

Proposed change (candidate diff sketch — refine in planning)

• In verify_task_body.py's concerns-audit check: for each <!-- concern-deferred: (?P<id>[a-z0-9-]+) --> in the body, look up the id in the task's concerns ledger;
• latest event == "addressed" (or id absent from ledger) -> WARN "stale concern-deferred marker '' — concern is addressed; remove or retag";
• latest event deferred/open -> current behavior unchanged. WARN-only (never a hard FAIL; forward-only).

Scope / surfaces

• Primary target: scripts/verify_task_body.py
• Update tests/test_verify_task_body.py with a stale-marker fixture.

Constraints / invariants

• Workflow-surface only; WARN-only; workflow_lint.py + ruff pass.

Provenance

• workflow_fix_target: scripts/verify_task_body.py
• fingerprint: a3f925bd4fab

Origin: clean-result-critic + codex-clean-result-critic v3 on #833, agreed procedural fix ("mechanizable: yes — a verifier WARN when a concern-deferred marker names a concern whose latest ledger event is addressed").