sane-sysload: fix battery logic to also work on Pinephone Pro (and more devices, generally)

pkgs/by-name/sane-sysload/sane-sysload

@@ -30,6 +30,7 @@ and some presets, encapsulating the above:
 
 import argparse
 import logging
+import os
 import time
 
 from dataclasses import dataclass
@@ -347,9 +348,18 @@ def try_battery_path(p: str) -> BatteryInfo | None:
     return BatteryInfo(ps.capacity, charges_per_hour, ps.status)
 
 def try_all_batteries() -> BatteryInfo | None:
-    p = try_battery_path("/sys/class/power_supply/axp20x-battery")  # Pinephone
-    if p is None:
-        p = try_battery_path("/sys/class/power_supply/BAT0")  # Thinkpad
+    # Pinephone: /sys/class/power_supply/axp20x-battery
+    # Pinephone Pro: /sys/class/power_supply/rk818-battery
+    # Thinkpad: /sys/class/power_supply/BAT0
+    #
+    # some machines have other stuff in power_supply, like wireless mice, AC adapters, etc.
+    # those devices [almost?] always lack one of the fields of the internal battery, like `capacity`,
+    # and so are correctly ignored here.
+    p = None
+    for ps in os.listdir("/sys/class/power_supply"):
+        p = try_battery_path(f"/sys/class/power_supply/{ps}")
+        if p is not None:
+            break
 
     logger.debug(f"perc: {p.percent_charged if p else None}")
     logger.debug(f"charge: {p.percent_charged if p else None}")