Acer M5-481T fails Ghostty because Ivy Bridge HD 4000 tops out at
OpenGL 4.2 in Mesa; Ghostty needs 4.3 — a generation ceiling, not a
missing driver. Document that plus UEFI/x86_64, RAM, and storage floors
(Nix store generations + BTRFS snapper + hibernate swap≈RAM). Linked
from README, docs map, HARDWARE.md; #95 points here.
