Apply codex round-7 Phase 5 copy-edit fixes + refresh STATE.md

Mechanical copy-edit closing the OPEN/PARTIAL items from
paper/codex_review_gpt55_v4_round7.md; substantive empirical
content unchanged. Manuscript-splice items (strip internal draft
notes, update stale abstract-count note) deferred to final splice.

- Phase 4 prose §V-G + §III-K methodology: "candidate classifiers"
  -> "candidate checks" (closes round-7 m13 + Spot-check 3 wording leak)
- Phase 4 prose §II: remove placeholder caveat sentence at the LOOO
  paragraph (closes round-7 M6 + A4)
- References v3: add [42] Stone 1974, [43] Geisser 1975, [44] Vehtari
  et al. 2017 (44 entries; was 41) — backs the §II LOOO addition
- Round-7 review: add row-count clarification note (11 Major / 15
  Minor labelled rows vs. the prompt's 9/12 tally)
- STATE.md: refresh from stale Phase-2 snapshot to current Phase 5
  status — Phases 1-4 complete; codex rounds 1-7 closed at Minor
  Revision; pending Gemini + Opus rounds + round-2/3 convergence

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

paper/paper_a_references_v3.md

@@ -84,4 +84,10 @@
 
 [41] H. White, "Maximum likelihood estimation of misspecified models," *Econometrica*, vol. 50, no. 1, pp. 1–25, 1982.
 
-<!-- Total: 41 references (v2: 36 + 5 new statistical methods refs) -->
+[42] M. Stone, "Cross-validatory choice and assessment of statistical predictions," *J. R. Statist. Soc. B*, vol. 36, no. 2, pp. 111–147, 1974.
+
+[43] S. Geisser, "The predictive sample reuse method with applications," *J. Amer. Statist. Assoc.*, vol. 70, no. 350, pp. 320–328, 1975.
+
+[44] A. Vehtari, A. Gelman, and J. Gabry, "Practical Bayesian model evaluation using leave-one-out cross-validation and WAIC," *Stat. Comput.*, vol. 27, no. 5, pp. 1413–1432, 2017.
+
+<!-- Total: 44 references (v3: 41 + 3 new LOOO refs for v4 §II addition) -->