- 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