Helix Boot v0.6.1

Two more boot-menu themes, greyscale icons, and a folder of tools for a Mac.

• Standby and Poly dark join the theme list (./theme.sh --theme standby, or the Look… window in HelixBoot.exe). They are other people's GRUB themes, adapted for Ventoy, and show every tool's icon in shades of grey. Standby is now the plain choice, in place of Ventoy's own white look.
• The stick gets a Mac folder: 18 free utilities to run on a working Mac, Apple silicon included, kept current like every other tool.

Standby is by Llewelyn Trahaearn (GPL) and Poly dark by Andrei Shevchuk (MIT); each is credited in its folder with its licence.

Added

• Tools for a Mac, in a Mac folder on the stick with a README.txt: 18
  free utilities to run on a working Mac (EtreCheck, OnyX, Malwarebytes, the
  Objective-See tools, Stats, Macs Fan Control, coconutBattery,
  GrandPerspective, AppCleaner, SuperDuper!, TestDisk & PhotoRec, Mist,
  OpenCore Legacy Patcher, Chris Titus Tech's MacUtil), fetched, verified and
  kept current like everything else. platform = "mac" on an app puts it
  there, as downloaded, and packs carry them.
• Two more themes for theme.sh and the Look window, both other people's GRUB
  themes with their own layout, adapted for Ventoy: Standby (Llewelyn
  Trahaearn, GPL) and Poly dark (Andrei Shevchuk, MIT), each with a splash
  in its colours. A preset can now bring its own layout and fonts
  (standalone = true in preset.toml).
• Greyscale icons: --icons grey redraws every icon, yours included, in shades
  of grey. Standby and Poly dark use it by themselves: the icon choice now
  defaults to auto, the theme's own style, and --icons logos keeps colour.

Changed

• Standby is the plain choice, in place of Ventoy's own white look: "Off" is no
  longer on the theme list, and --theme off (or a stick that had it) gives
  Standby. theme = "" in local.toml still gives Ventoy's own look.

Fixed

• The look preview follows each theme's own layout, boxes and font sizes.