fix(brand): unify calligraphy logo across header, footer and brand page

- logo.svg: remove dark-mode white fill so header/hero calligraphy stays
  visible on white backgrounds and matches footer logo-white.svg
- about/brand: replace sans-serif brand title with BrandCalligraphyName,
  reusing the same AoyagiReisho SVG paths as the footer logo without
  loading the 4.4MB font file
- add unit tests for BrandCalligraphyName and document decision in CONTEXT.md

src/app/(marketing)/about/brand/brand-content.tsx

@@ -2,6 +2,7 @@
 
 import { motion } from 'framer-motion';
 import { ScrollReveal } from '@/components/ui/scroll-reveal';
+import { BrandCalligraphyName } from '@/components/ui/brand-calligraphy-name';
 import {
   ArrowRight,
   Target,
@@ -91,11 +92,15 @@ export default function BrandContent() {
               initial={{ opacity: 0, y: 40 }}
               animate={{ opacity: 1, y: 0 }}
               transition={{ duration: 0.8, delay: 0.2, ease: EASE_OUT }}
-              className="text-4xl sm:text-5xl md:text-6xl lg:text-7xl xl:text-8xl font-black text-ink leading-[0.92] tracking-tightest mb-8 sm:mb-10"
+              className="text-4xl sm:text-5xl md:text-6xl lg:text-7xl xl:text-8xl text-ink leading-[1.05] tracking-tight mb-8 sm:mb-10"
             >
-              睿新致远
+              <span className="sr-only">睿新致遠</span>
+              <BrandCalligraphyName
+                className="block h-[0.95em] w-auto text-ink"
+                ariaHidden
+              />
               <br />
-              <span className="text-brand">以技术驱动业务增长</span>
+              <span className="text-brand font-black">以技术驱动业务增长</span>
             </motion.h1>
 
             {/* 数据条 */}

src/components/ui/brand-calligraphy-name.test.tsx

@@ -0,0 +1,31 @@
+import { describe, it, expect } from '@jest/globals';
+import { render } from '@testing-library/react';
+import '@testing-library/jest-dom';
+import { BrandCalligraphyName } from './brand-calligraphy-name';
+
+describe('BrandCalligraphyName', () => {
+  it('renders the four calligraphy glyph paths from the logo asset', () => {
+    const { container } = render(<BrandCalligraphyName />);
+    const svg = container.querySelector('svg');
+    expect(svg).toBeInTheDocument();
+    expect(svg).toHaveAttribute('viewBox', '0 -40 200 48');
+    expect(svg!.querySelectorAll('path')).toHaveLength(4);
+    expect(svg!.querySelectorAll('path')[0]!.getAttribute('d')).toContain('M 378.00 62.00');
+    expect(svg!.querySelectorAll('path')[3]!.getAttribute('d')).toContain('M 799.00 85.00');
+  });
+
+  it('is exposed as an image with a brand label by default', () => {
+    const { container } = render(<BrandCalligraphyName />);
+    const svg = container.querySelector('svg');
+    expect(svg).toHaveAttribute('role', 'img');
+    expect(svg).toHaveAttribute('aria-label', '睿新致遠');
+  });
+
+  it('can be hidden from assistive technology when paired with sr-only text', () => {
+    const { container } = render(<BrandCalligraphyName ariaHidden />);
+    const svg = container.querySelector('svg');
+    expect(svg).toHaveAttribute('aria-hidden', 'true');
+    expect(svg).not.toHaveAttribute('role');
+    expect(svg).not.toHaveAttribute('aria-label');
+  });
+});