Stop resolve_remote_scripts_dir silently returning the local path as the partner's

SSH_TIMEOUT comes from the calling script, so a caller without it made timeout fail before ssh ran; with stderr discarded the fallback then named this host's SCRIPTS_DIR as the remote's.

common.sh

@@ -848,12 +848,28 @@ read_remote_conf_array() {
 resolve_remote_scripts_dir() {
     local ip="$1" ssh_key="${2:-$SSH_KEY}" strict_host_key="${3:-yes}"
     local probe_cmd result
-    local -a opts=(-o ConnectTimeout="$SSH_TIMEOUT" -o BatchMode=yes)
+    # SSH_TIMEOUT is set by the calling script, not by any conf, so a caller that forgets it
+    # hands `timeout` an empty interval — which fails instantly, before ssh is ever run. With
+    # stderr discarded the failure is invisible and the fallback below then returns THIS host's
+    # SCRIPTS_DIR as though it were the partner's. Every use of the result is a remote path, so
+    # the caller goes on to run commands against a directory that exists here and not there.
+    # That is how Step 1b ended up pointing at /boot on an appdata mirror.
+    local _to="${SSH_TIMEOUT:-15}"
+    local -a opts=(-o ConnectTimeout="$_to" -o BatchMode=yes)
     [[ "$strict_host_key" == "no" ]] && opts+=(-o StrictHostKeyChecking=no)
     probe_cmd=$(platform_scripts_dir_probe_cmd)
-    result=$(timeout "$SSH_TIMEOUT" ssh -i "$ssh_key" "${opts[@]}" root@"$ip" "$probe_cmd" \
+    result=$(timeout "$_to" ssh -i "$ssh_key" "${opts[@]}" root@"$ip" "$probe_cmd" \
         2>/dev/null | tr -d '[:space:]')
-    echo "${result:-$SCRIPTS_DIR}"
+
+    # A probe that answered is the only thing trusted. The fallback stays — callers need a path
+    # to name in an error message — but it is announced, because "we could not ask the partner
+    # where it keeps its scripts" and "the partner keeps them where we do" are different facts
+    # and were being reported identically.
+    if [[ -z "$result" ]]; then
+        warn "Could not read SCRIPTS_DIR from $ip — assuming $SCRIPTS_DIR, which is wrong if it runs from appdata" >&2
+        result="$SCRIPTS_DIR"
+    fi
+    echo "$result"
 }
 
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