verify_plan: WARN when a plan registers a test-retest kappa demotion gate while pinning judge temperature 0

Goal

Add a WARN-level check to scripts/verify_plan.py (alongside the c27 gate-arithmetic family) that fires when a plan text (a) registers a test-retest reliability gate — test-retest (or test retest/retest) co-occurring with κ/kappa and a demotion/threshold clause — AND (b) pins temperature 0 (or temperature=0 / temp 0) in the same judged-DV / judge-wave section.

Why (incident)

#2202 plan v1 (2026-08-08, Statistics critic blocker): the plan pinned its Sonnet label wave at temperature 0 while registering a "200-item test-retest → κ per mode; κ<0.6 demoted to report-only" gate sourced to the #1738 convention. The parent instrument ran at API-default temperature (temperature 1.0, scripts/issue1738_characterize.py:326); its meaningful κ range (0.786–0.982) exists because sampled outputs vary across draws. At temperature 0 a byte-identical retest returns near-identical output — κ≈1 for every mode, the demotion gate can never fire, and the threshold is uncalibrated for the temp-0 surface. The gate was the SOLE instrument-validity screen for novel data-derived labels carrying BH-tested rate headlines: a gate that can only pass is a false positive by construction. This is the threshold-transplanted-across-read-surfaces failure family and is likely to recur in any judged-labeling plan.

A second, related trap worth a companion clause in the same check (or the WARN detail text): a rubric-keyed judge CACHE serving the first-pass verdict back to the retest row makes κ≡1 exactly at ANY temperature — the WARN detail should remind that retest rows need a distinct custom-id prefix (e.g. the #1738 rt_ convention, scripts/issue1738_characterize.py:303) or a fresh cache_dir.

Acceptance

• New check id (next free c<NN> slug, e.g. c48_retest_kappa_temp0), WARN-only, with a standalone N/A escape phrase (e.g. N/A — no test-retest gate) recognized by _standalone_na_declared.
• Detection is regex/section-scoped over the plan text (~5–15 lines), no semantic parsing; false-positive tolerant (WARN, never FAIL).
• Unit tests in tests/test_verify_plan.py: fires on the #2202 v1 shape (retest+κ gate + temp 0 in same section); silent when temperature is API-default/unpinned; silent when the N/A phrase is declared; silent when retest and temp-0 appear in unrelated sections (best-effort scoping).
• workflow_lint.py --check-lessons-index untouched (no new rule file needed); verify_plan docstring check-list updated.

Provenance

Surfaced by the Statistics & Measurement critic on #2202 plan v1 (session cf372c0b, 2026-08-08) as an explicit workflow-fix prose follow-up; filed by the #2202 orchestrator per .claude/rules/workflow-fix-on-bug.md (surfaced-prose follow-ups auto-file + spawn).