Helix Boot v0.6.3

New default icons. Every tool, category and Ventoy entry in the boot menu now has an icon from one glossy set, on every theme. The previous set is still there: ./theme.sh --icons classic, or Icons: Classic in the Windows app's Look window.

Also: a stick keeps its own icons and splash when it is updated from a PC that has none of its own.

Changed

• New default icons: every tool, category and Ventoy entry now has an icon
  from one glossy set, the HELIXBOOT icon collection, the same on every theme
  (the presets no longer recolour the category icons). The set before it, each
  tool's own logo with flat category icons, is the classic icon pack:
  ./theme.sh --icons classic. Masters are in docs/artwork/helix-icons/.
• A stick keeps its own icons and splash (the ones from a byo/ folder) when it
  is updated from a PC that has none of its own, instead of getting the stock
  ones back. The PC that put them there still replaces or removes them.