fix: teardown-host refuses a terminal-less run instead of aborting mute

host/teardown-host.sh had no `[ -t 0 ]` check before its confirmation
prompt. Without --yes/BOX_YES and without a terminal — CI, a pipe, a
nohup — it fell into `read`, took the instant EOF and exited 1 saying
only "aborted": a refusal naming neither the cause nor the override, in
the most destructive script in the tree.

It now refuses with the override named, exit 2 — "you invoked this
wrong", matching host/revoke-user.sh --purge and install.sh's confirm(),
versus 1 for "you were asked and you said no".

The gate sits below the --yes/BOX_YES arm, so consent given
non-interactively still runs headless, and above the first incus call,
so the refusal needs no daemon — which is what lets test/cli.sh drive it
for real instead of grepping for it.

Refs #113

CHANGELOG.md

@@ -154,6 +154,21 @@ which records not just what changed but what each drill run proved.
   wrong default: it is the only thing to roll back *to*, at exactly the
   moment that matters. No behaviour change.
 
+- **`teardown-host.sh` refuses a terminal-less run instead of aborting mute**
+  (#113) — the most destructive script in the tree was the one that would not
+  tell a non-interactive caller how to proceed. With no `--yes`/`BOX_YES` and
+  no TTY it fell straight into `read`, took the instant EOF and exited 1
+  saying only `aborted` — a refusal that names neither the cause nor the
+  override. It now checks `[ -t 0 ]` and refuses with
+  `--yes (or BOX_YES=1) means yes.`, exit **2** — "you invoked this wrong",
+  the same contract and the same code as `host/revoke-user.sh --purge` and
+  `install.sh`'s `confirm()`, versus 1 for "you were asked and you said no".
+  The gate sits *below* the `--yes`/`BOX_YES` arm, so consent given
+  non-interactively still runs headless — CI's uninstall drill and
+  `box uninstall --purge-host --force` forward `--yes` and are unaffected —
+  and *above* the first `incus` call, so the refusal costs no daemon and
+  `test/cli.sh` drives it for real rather than grepping for it.
+
 ## 0.8.0 — 2026-07-19
 
 ### Added

host/teardown-host.sh

@@ -28,6 +28,18 @@ $purge && echo "Incus itself will also be uninstalled (--purge-incus)."
 if [ "$yes" -eq 1 ]; then
   echo "(confirmed non-interactively: --yes/BOX_YES)"
 else
+  # No terminal to ask on, and no consent given: refuse and say how to proceed,
+  # rather than fall into 'read', hit instant EOF and abort with nothing but
+  # "aborted" (#113). This must stay BELOW the --yes/BOX_YES arm above — the
+  # order is the contract: consent given non-interactively still runs headless
+  # (CI's uninstall drill and 'box uninstall --purge-host --force' depend on
+  # it), consent NOT given without a terminal is a usage error, exit 2, the
+  # same shape as host/revoke-user.sh and install.sh. It also lands before the
+  # first 'incus' call below, so the refusal needs no daemon.
+  if [ ! -t 0 ]; then
+    echo "teardown-host: refusing to run without a terminal to confirm on. --yes (or BOX_YES=1) means yes." >&2
+    exit 2
+  fi
   # EOF (Ctrl-D) refuses, out loud: unguarded, errexit would end the run on
   # this line and the 'aborted' below would never print (#111).
   read -rp "Continue? [y/N] " a || { echo "aborted"; exit 1; }

test/cli.sh

@@ -1993,6 +1993,11 @@ check "teardown-host: honors --yes/BOX_YES (CI runs it unattended)" 0 "" \
   grep -qF 'BOX_YES' "$ROOT/host/teardown-host.sh"
 check "teardown-host: points at box uninstall when done" 0 "" \
   grep -qF "box uninstall" "$ROOT/host/teardown-host.sh"
+# ...and the other side of that contract (#113): consent NOT given and no
+# terminal to ask on is a usage error, not a mute 'aborted'. Driven for real —
+# the gate sits above the first 'incus' call, so a daemon-free run reaches it.
+check "teardown-host: refuses without a TTY and names the override (#113)" 2 \
+  "--yes (or BOX_YES=1) means yes" bash "$ROOT/host/teardown-host.sh" </dev/null
 
 # #102's race, in the one other file that sets pipefail. A daemon-free run
 # cannot exercise a UFW teardown, so the shape is pinned instead: no `ufw