Add radial-spotlight-glow detector rule

Flags the decorative low-opacity chromatic radial-gradient "spotlight"
washed behind a hero or section and fading to transparent, an AI-slop
reflex the saturated radial-halo gate lets slip (e.g. rgba(80,111,255,
0.26) -> transparent on a mobile hero).

Gates: a non-repeating radial-gradient whose last stop is transparent,
whose visible stops are all low-opacity (alpha < 0.45) with at most two
of them, at least one chromatic (channel spread >= 24 exempts neutral
vignettes), on a decorative-scale surface (width >= 240, height >= 160,
exempting badges/avatars/small lights). The alpha band is disjoint from
radial-halo (>= 0.7), so the two never double-report.

Wired into both element loops (static-html + injected browser) with the
pure checkRadialSpotlight shared by both adapters. TDD fixture with 5
flag / 9 pass shapes. Browser-path sweep over the eval corpus: 29 hits
on 11 pages, 0 false positives. Count 59 -> 60.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

cli/engine/registry/antipatterns.mjs

@@ -149,6 +149,15 @@ const ANTIPATTERNS = [
     skillSection: 'Color & Contrast',
     skillGuideline: 'dark mode with glowing accents',
   },
+  {
+    id: 'radial-spotlight-glow',
+    category: 'slop',
+    name: 'Decorative radial spotlight glow',
+    description:
+      'A soft, low-opacity accent-colored radial gradient fading to transparent, dropped behind a hero or section as a "spotlight." It is a reflex AI decoration — the translucent cousin of the saturated radial halo. Let the surface stand on its own, or light the composition with a deliberate material accent rather than a floating colored haze.',
+    skillSection: 'Color & Contrast',
+    skillGuideline: 'dark mode with glowing accents',
+  },
   {
     id: 'marquee',
     category: 'slop',