workflow-fix: verify_task_body check-31 per-unit pattern set gains pair

Overview / Motivation

Auto-filed by the workflow-fix-on-bug protocol from a mechanizable: yes prose follow-up in the clean-result-critic's verdict on task #1415 (epm:clean-result-critique v5, Lens 11 finding; emitting agent: clean-result-critic; router: orchestrator).

Goal

Add perpair (and per-pair) to verify_task_body.py check 31's per-unit figure filename pattern set so an embedded per-pair panel is recognized.

Workflow gap

• Bug observed: check 31's per-unit filename pattern set misses the perpair naming used by the issue1415 per-pair small-multiples figures, so the mechanical check cannot see an embedded per-unit view under that name.
• Why it is a workflow gap: _PER_UNIT_FIG_RE = re.compile(r"(?<![a-z0-9])per[-_]?(context|unit|cell)") (scripts/verify_task_body.py:2445) omits pair from the alternation; per-PAIR is this project's most common per-unit grain (the pair is the inference unit on the #1415 line), so both arms of check 31 (orphaned-committed-per-unit WARN and the critic's Lens-11 keying) are blind to position_profile_perpair_*.png-style figures. The clean-result-critic caught #1415's Lens-11 break manually; the mechanical check should have.
• Confidence (emitter): high
• verified-at-filing: grep -n "perpair\|per_pair\|percell" scripts/verify_task_body.py → 0 hits for pair-form patterns; sed -n '2445p' shows the alternation (context|unit|cell) (2026-07-23). Presence claim on the named target confirmed (the regex exists at the cited line; pair absent).

Proposed change (candidate diff sketch — refine in planning)

• PER_UNIT_FIG_RE = re.compile(r"(?<![a-z0-9])per[-]?(context|unit|cell)", re.IGNORECASE)

• PER_UNIT_FIG_RE = re.compile(r"(?<![a-z0-9])per[-]?(context|unit|cell|pair)", re.IGNORECASE) (+ pin test: a *_perpair_*.png committed-but-unembedded fixture WARNs; an embedded one PASSes; verify the indiv exclusion note stays intact)

Scope / surfaces

• Primary target: scripts/verify_task_body.py
• Check tests/test_verify_task_body.py check-31 fixtures; update the SPEC.md check-31 prose if it enumerates the patterns.

Constraints / invariants

• Workflow-surface only. Existing check-31 semantics (WARN never FAIL; the #1510 exemption idioms; the indiv exclusion) unchanged.
• This session runs under EPM_WORKFLOW_FIX_SESSION=1 and carries a workflow_fix_target: Provenance line — recursion guard applies.

Provenance

• workflow_fix_target: scripts/verify_task_body.py
• fingerprint: 1402fa9ef2e1

target_file: scripts/verify_task_body.py bug_observed: check 31's per-unit filename pattern set misses the perpair naming used by the issue1415 per-pair small-multiples figures, so the mechanical check cannot see an embedded per-unit view under that name why_workflow_gap: _PER_UNIT_FIG_RE omits pair from its alternation while per-pair is the project's most common per-unit grain; the critic had to catch a Lens-11 break the mechanical check should have keyed on proposed_change: add perpair (and per-pair) to verify_task_body.py check 31's per-unit figure filename pattern set so an embedded per-pair panel is recognized diff_sketch: |

• per[-_]?(context|unit|cell)

• per[-_]?(context|unit|cell|pair)
• check-31 fixture for perpair.png confidence: high related_task: #1415