post: QR pre-download decode gate (EN+ZH) + Argon batch-10 review

- 69-module symbol at 20 mm = 0.29 mm/module, refused below a 0.40 mm floor
- 30% centre image on a 29-module symbol knocks out 19% of area, capped at 15%
- maroon #800000 passes WCAG at 10.9:1 but is 1.9:1 on the red channel, so warn only
- 300 dpi export quoted at 50.1 x 56.9 mm with the caption band and pHYs block
- gate reads every code back with jsQR at two densities before the download unlocks
- batch-10 external review: 94/96/88/100, 10 items applied, 2 rejected with reasons

scripts/og-gen/art-meta.json

@@ -369,5 +369,10 @@
   "evidence": "6 seats - 9 s - 403 to 502 mapping",
   "ogTitle_en": "The Gateway That Tripped Trust & Safety",
   "ogTitle_zh": "网关撞上风控"
+ },
+ "qr-gate-that-decodes-before-the-download": {
+  "evidence": "69 modules @ 20 mm · 0.29 mm/module · floor 0.40 mm",
+  "ogTitle_en": "Decode Before Download",
+  "ogTitle_zh": "先解码，再给下载"
  }
 }