- sim.png regenerated from sim.svg with true transparency (was flattened
onto opaque white; favicon showed a white box)
- new favicon.svg: same glyph, fill moved to presentation attribute +
embedded @media (prefers-color-scheme: dark) -> white glyph on dark
browser themes (interface sim.svg untouched, keeps dark:invert)
- index.html: dual icon links (svg for modern browsers, png Safari fallback)
- sw.js: precache favicon.svg, cache bump otaman-v11 -> otaman-v12
