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/engines/static-html/detect-html.mjs

@@ -24,6 +24,7 @@ import {
   checkElementMotion,
   checkElementOversizedH1,
   checkElementQuality,
+  checkElementRadialSpotlight,
   checkCreamPalette,
   checkHtmlPatterns,
   checkNumberedSectionLabelsFromDoc,
@@ -105,6 +106,7 @@ const STATIC_ELEMENT_RULES = [
   { id: 'oversized-h1', selector: 'h1', run: (el, tag, style, window) => checkElementOversizedH1(el, style, tag, window) },
   { id: 'clipped-overflow-container', selector: '*', run: (el, tag, style, window) => checkElementClippedOverflow(el, style, tag, window) },
   { id: 'gpt-thin-border-wide-shadow', selector: '*', run: (el, tag, style) => checkElementGptBorderShadow(el, style) },
+  { id: 'radial-spotlight-glow', selector: '*', run: (el, tag, style, window) => checkElementRadialSpotlight(el, style, tag, window) },
 ];
 
 async function detectHtml(filePath, options = {}) {