Follow-up to #7435, which fixed _smart_apt_install. Three sites were left.
studio/setup.sh: the WSL GGUF build-deps block is the pre-#7435 install.sh
pattern verbatim. It probes with 'test -r /dev/tty', assumes REPLY=y when that
fails, and then runs the elevated apt-get with stdin open. Its own guard
comment says a password is needed on WSL, so this is exactly the scenario from
issue #7307, and install.sh runs setup.sh in the same install. Give it the same
treatment: a real open probe, -n -k with stdin closed on the headless path, and
the manual command plus the existing _SKIP_GGUF_BUILD degradation on failure.
The helper is defined locally because setup.sh runs as its own process.
install.sh autostart prompt: still used 'test -r /dev/tty' and printed the
question before checking, leaving a dangling prompt in container logs. Reuse
_can_read_tty and move the printf inside the branch.
install.sh interactive escalation: a sudoers denial, a wrong password or an apt
error aborted on the bare message while the headless branch printed what to run
by hand. Make both symmetric.
Co-authored-by: danielhanchen <unslothai@gmail.com>