feat(home): Hero 动态粒子层（入场浮现后静止）

新增 hero-particle-field 组件作为 Hero L3 层：品牌红点缀、Canvas + rAF
仅在 ~600ms 入场窗运行后冻结为静态帧，遵守「无持续循环动画」动效铁律；
prefers-reduced-motion 退化为一次性静态帧。固定种子 PRNG 保证视觉快照可复现。
同步更新 home-content-v15 接入与单测、home 视觉基线。

Co-Authored-By: 阿睿 <workbuddy@tencent.com>

src/app/(marketing)/home-content-v15.test.tsx

@@ -98,6 +98,16 @@ describe('HomeContentV15 - 浅色 Hero（暗黑模式 token 友好）', () => {
     expect(hero.querySelector('img')).toBeNull();
   });
 
+  it('mounts the brand-red dynamic particle layer (entrance-only, no continuous loop)', () => {
+    render(<HomeContentV15 />);
+
+    const hero = screen.getByTestId('hero-section');
+    const particles = screen.getByTestId('hero-particle-field');
+    expect(particles.tagName).toBe('CANVAS');
+    expect(particles).toHaveAttribute('aria-hidden', 'true');
+    expect(hero.contains(particles)).toBe(true);
+  });
+
   it('keeps a single primary CTA and demotes the secondary action to a text link', () => {
     render(<HomeContentV15 />);
 

src/app/(marketing)/home-content-v15.tsx

@@ -6,6 +6,7 @@ import { ScrollReveal, StaggerReveal } from '@/components/ui/scroll-reveal';
 import { Badge } from '@/components/ui/badge';
 import { StaticLink } from '@/components/ui/static-link';
 import { HeroProductVisual } from '@/components/sections/hero-product-visual';
+import { HeroParticleField } from '@/components/sections/hero-particle-field';
 import { ArrowRight, Lightbulb, Database, Layers, Code, Puzzle, Server, Quote, Calendar } from 'lucide-react';
 import { cn } from '@/lib/utils';
 import { EASE_OUT } from '@/components/ui/page-decoration';
@@ -177,6 +178,9 @@ function HeroSection({ heroData }: {
       {!reduceMotion && (
         <div ref={spotRef} className="absolute inset-0 pointer-events-none hero-dot-spot opacity-60" aria-hidden="true" />
       )}
+      {/* L3 动态粒子（品牌红点缀）：入场浮现后静止，rAF 仅跑 ~600ms，无持续循环；
+           reduced-motion 下退化为一次性静态帧 */}
+      <HeroParticleField />
 
       <div className="max-w-container mx-auto px-4 sm:px-6 lg:px-10 relative z-10 w-full py-16 sm:py-20 md:py-24 lg:py-24">
         <div className="grid items-center gap-16 lg:grid-cols-[1.05fr_0.95fr]">