daily-fix: planner authors Row-coverage with paired contrast

Overview / Motivation

Auto-filed by the /daily 2026-07-08 problem sweep (transcript-mined; emitting agent: /daily orchestrator).

Goal

Stop the recurring c18 bounce by making Row-coverage authoring guidance explicit in the planner spec.

Workflow gap

• Bug observed: Transcript 05000ba2 (issue-1112) 10:08:07Z: FAIL c18_paired_contrast_source_coverage on plan v4->v5; 13:07:30Z the SAME FAIL again on v7, fixed in v8 — two mechanical bounces in one day on one task.
• Why it is a workflow gap: The mechanical gate exists but no planner-side spec line tells planners to write the Row-coverage block when registering a paired contrast, so it is systematically discovered post-hoc.
• Confidence (emitter): medium

Proposed change (candidate diff sketch — refine in planning)

• In the amendment/delta-scoped plan guidance: "Any registered paired contrast MUST carry its Row-coverage: per-arm rows at authoring time — verify_plan c18 FAILs otherwise (2x on #1112, 2026-07-08)."

Scope / surfaces

• Primary target: .claude/agents/planner.md
• Grep the workflow surface for the pattern before editing and update every hit; list them in the plan.

Constraints / invariants

• Workflow-surface only — never experiment code, configs/, or tasks/.
• scripts/workflow_lint.py --check-asks + --check-references pass; 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 its own subagents' workflow-fix candidates (recursion guard).

Provenance

• workflow_fix_target: .claude/agents/planner.md
• origin: transcript-mined by /daily 2026-07-08 problem sweep
• evidence: mine-A P3 (05000ba2 10:08:07Z, 13:07:30Z)