workflow-fix: durable-output check before reviewer no-show fallback

Overview / Motivation

Auto-filed by the workflow-fix-on-bug protocol from a workflow-fix candidate raised on task #810 (emitting agent: orchestrator, /issue 810 session).

Goal

At ensemble verdict collection (Step 5b and the analogous 9a/9a-bis reads), check for durable outputs (a posted verdict marker or a written verdict file) before treating a subagent thrash-death/error notification as a reviewer no-show.

Workflow gap

• Bug observed: the orchestrator misread a thrash-killed code-reviewer as a no-show and adopted a unilateral ensemble decision (FAIL from the Codex verdict alone), although the reviewer's PASS verdict had ALREADY been durably posted as epm:code-review v4 — only the agent's final summary turn died of autocompact thrash. The orchestrator had to post a corrective marker and route to the reconciler after the fact (task #810, 2026-07-02, ~09:25Z).
• Why it is a workflow gap: SKILL.md Step 5b instructs reading both markers from events.jsonl, but the failure-handling prose (the "Codex twin no-show fallback") keys on the Agent-tool completion RESULT, not on durable task state; an agent whose work is durable but whose final turn dies (autocompact thrash — a recurring class: 3 such deaths on #810 alone) is indistinguishable from a genuine no-show unless the orchestrator re-reads events.jsonl / the verdict temp file first.
• Confidence (emitter): high

Proposed change (candidate diff sketch — refine in planning)

+ In Step 5b (and the 9a / 9a-bis ensemble reads), when an Agent-tool
+ completion result reports an error/thrash death for a reviewer subagent,
+ BEFORE invoking any no-show fallback or unilateral decision:
+   1. Re-read the task's events.jsonl for the expected verdict marker
+      (epm:code-review v<n> / twin / critique kinds) posted after the
+      dispatch breadcrumb; and
+   2. Check the conventional verdict temp file (/tmp/issue-<N>-...-v<n>.md).
+ If either exists and conforms, treat the reviewer as RETURNED and use the
+ durable verdict; a thrash-killed summary turn is not a no-show.

Scope / surfaces

• Primary target: .claude/skills/issue/SKILL.md
• Grep the workflow surface for the pattern before editing (grep -rln 'no-show' .claude/ CLAUDE.md scripts/) and update every relevant ensemble-read site; list them 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; if workflow.yaml or CLAUDE.md change, they stay consistent with the rule file.
• 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: .claude/skills/issue/SKILL.md
• fingerprint: c73d5e2c53ed

Surfaced prose (verbatim): "the orchestrator should check for durable outputs (posted markers / written verdict files) before treating a thrash-death notification as a reviewer no-show" — raised in #810 epm:progress corrective note, 2026-07-02.