brand: sync vit mark/wordmark SVGs and update inline viewBoxes across docs
Update all brand SVGs from the extro master (tight viewBoxes replacing
0 0 32 32 / 0 0 56 34). Update inline SVG viewBoxes in all HTML files:
wordmarks 0 0 56 34 → 3.75 3 49 25.75, marks 0 0 32 32 → 3.375 2.5 25.25 25.25.
Reduce header wordmark height 28→24 and README wordmark height 48→40 to
compensate for ~15% visual size increase from tight viewBox.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>