feat(sensors): numeric -n mode + lmsensors_n extend for HA SNMP migration [#618]

dcinfra/sensors/temper/lmsensors-extend.sh

@@ -37,6 +37,39 @@ format_block() {
 }
 
 # True when a TEMPer USB dongle (0c45:7401) is attached and the venv exists.
+
+# Numeric mode: print ONE Celsius float for snmpd extend lmsensors_n [#618].
+# Preference: TEMPer external > TEMPer internal > first native/sysfs temp
+# reading. Consumed by HA's SNMP config-entry integration (device_class
+# temperature; HA renders C in the instance display unit).
+numeric_pick() {
+    local internal="${1:-}" external="${2:-}" native="${3:-}" pick
+    local num_re='^-?[0-9]+(\.[0-9]+)?$'
+    for pick in "$external" "$internal"; do
+        pick="${pick#+}"
+        [[ "$pick" =~ $num_re ]] && { printf '%s\n' "$pick"; return 0; }
+    done
+    if [[ -n "$native" ]]; then
+        pick="$(grep -oE '\-?[0-9]+(\.[0-9]+)?' <<<"$native" | head -1)"
+        [[ "$pick" =~ $num_re ]] && { printf '%s\n' "$pick"; return 0; }
+    fi
+    return 1
+}
+
+numeric_main() {
+    local internal external line
+    if has_temper_probe; then
+        if read -r internal external <<<"$(read_temper 2>/dev/null)"; then
+            numeric_pick "${internal:-}" "${external:-}" "" && return 0
+        fi
+    fi
+    line="$(run_native_sensors | grep -m1 '°C')"
+    [[ -n "$line" ]] && numeric_pick "" "" "$line" && return 0
+    line="$(read_sysfs_thermal 2>/dev/null | head -1 | awk '{printf "+%.1f°C", $2/1000}')"
+    [[ -n "$line" ]] && numeric_pick "" "" "$line" && return 0
+    echo "error: numeric mode found no sensor source" >&2
+    return 1
+}
 has_temper_probe() {
     command -v lsusb >/dev/null 2>&1 || return 1
     [[ -x "$VENV_PY" ]] || return 1
@@ -130,5 +163,5 @@ main() {
 }
 
 if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
-    main
+    if [[ "${1:-}" == "-n" ]]; then numeric_main; else main; fi
 fi