Vendor the vector logo from the legacy branch
(modules/nixos/branding/logo.svg) and use it for the live ISO's isolinux
splash: rsvg-convert renders it, recolored to the palette accent and
centred on the theme base (from theme-state.json) at build time, wired via
isoImage.splashImage in hosts/live.nix. Verified the generated PNG by
building it in the sandbox.
UEFI/GRUB still uses the stock theme (grubTheme needs a full theme dir —
left on the roadmap), as does the distroId switch.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
