AI Performance remaining article audit

Reviewed on 2026-08-02:

• pages/ds/primary-data.md: already uses an answer-first definition, a primary/secondary comparison table, acquisition-source judgment rules, examples, traps, and a concise exam summary. No forced rewrite.
• pages/ds/z-score-method.md: already separates z-score, standardization, deviation score, and outlier detection; includes conditions and cautions for the ±2 to ±3 rule. No forced rewrite.
• pages/gk/vq-vae.md: already emphasizes discrete latent representation, vector quantization, codebook selection, and comparisons with VAE, β-VAE, CVAE, and GAN. No forced rewrite.
• pages/sg/jvn.md: revised because its former structure was less consistent and its distinction among JVN, JVN iPedia, CVE, CVSS, IPA, and JPCERT/CC could be made more extractable.