Drop the host expect dependency from the PS/2, timer, IOMMU, and USB
storage (BOT) runtime proofs. local/scripts/qemu-login-expect.py drives
the guest over serial-on-stdio with ordered expect/send steps, per-step
timeouts (matching expect's per-pattern semantics), and pass/fail markers.
It distinguishes premature QEMU death (exit 3) from genuine check failure
(exit 1) so the scripts retry external interruptions without retrying real
failures. Scripts use headless -display none -vga none (fbcond serial
mirror), a 3600s per-step timeout, and a retry loop (max 5 attempts).
