Show battery power draw from sensors in waybar

Replace the built-in battery module with a custom/battery script that
combines sysfs capacity/status with the power1 reading from `sensors`,
displaying it as "85% (5.4W)" next to the icon.

config/waybar/scripts/battery-power.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+set -Eeuo pipefail
+
+bat_dir="/sys/class/power_supply/BAT0"
+capacity=$(<"$bat_dir/capacity")
+status=$(<"$bat_dir/status")
+
+power=$(sensors -j 2>/dev/null | python3 -c '
+import json, sys
+data = json.load(sys.stdin)
+for chip, fields in data.items():
+    if not chip.startswith("BAT"):
+        continue
+    power1 = fields.get("power1")
+    if power1:
+        print(round(next(iter(power1.values())), 1))
+        break
+')
+
+text="${capacity}%"
+[[ -n "$power" ]] && text+=" (${power}W)"
+
+icons=("󰁺" "󰁼" "󰁾" "󰂀" "󰁹")
+if [[ "$status" == "Charging" ]]; then
+  icon="󰂄"
+else
+  idx=$((capacity * ${#icons[@]} / 101))
+  icon="${icons[$idx]}"
+fi
+
+class="normal"
+if [[ "$status" != "Charging" ]]; then
+  if ((capacity <= 15)); then
+    class="critical"
+  elif ((capacity <= 30)); then
+    class="warning"
+  fi
+fi
+
+printf '{"text": "%s %s", "class": "%s", "tooltip": "%s, %s"}\n' \
+  "$icon" "$text" "$class" "$status" "${power:+${power}W}"