ce5fa09a95
Two critical bugs prevented the hypervisor boot path from working:
1. GRUB2 EFI requires explicit gpt/msdos prefix in partition names.
The shorthand (hd0,2) does NOT resolve for GPT disks. Fixed by
having vt_load_part_table set hiso_iso_part/hiso_efi_part with
correct notation based on detected partition table type.
2. hiperiso_boot C function wrapped $hiso_efi_part in extra parens:
($hiso_efi_part) expanded to ((hd0,gpt2)) which GRUB2 parsed as
device name (hd0,gpt2) with literal parens. Fixed by using
${hiso_efi_part} without wrapping.
QEMU-verified: kernel boots, loads initramfs, runs /init with all
hiperiso_* parameters correctly passed through kernel cmdline.