master grew _pick_asset() while this branch grew a second answer to the
same question inside install_program(). Two functions deciding which
archive this machine wants is one too many, so the managed build is
asked for at the top of the picker: Dikte's own Vulkan whisper-server
first where the machine is one it is built for, then upstream's newest,
then the nightly pointer, then the newest release that carries a build.
install_program() is back to master's three lines and reads which of the
two landed off the asset name.