## What happened

`omarchy-battery-status` reports on a single battery pack, so on machines with
more than one battery the power panel's text shows the state of whichever pack
`upower -e` lists first rather than the state of the machine.

The selection is here:

```bash
battery=$(upower -e 2>/dev/null | grep BAT | head -n 1)
```

`head -n 1` picks `BAT1`. On a Surface Book 2 that is the small tablet battery
(23.2 Wh design), not the 62.2 Wh base battery that supplies most of the
runtime. The SB2 also drains the base first and leaves the tablet pack parked,
so the pack that gets reported is typically the one sitting at a flat
percentage with `power_now` = 0 for hours.

The `cycle_count` and charge-threshold fallbacks have the same issue:

```bash
cycles=$(cat "$power_supply_path"/BAT*/cycle_count 2>/dev/null | head -1)
```

## What was expected

The figures in the power panel should describe the whole machine, and should
agree with the bar icon.

They currently don't, because the QML and the shell script disagree about the
data source. `panels/power/Panel.qml` reads `UPower.displayDevice` — UPower's
aggregate device, which sums energy across packs and is correct — for the
icon, `batteryFraction`, and the low-battery warning in
`services/battery/Service.qml`. Only the panel's *text* comes from
`omarchy-battery-status`.

The visible result is that the panel's hero percentage (`Panel.qml:375`,
from the script) and the progress bar directly beneath it (`Panel.qml:408`,
from `batteryFraction`) show two different numbers at the same time.

## Steps to reproduce

On any machine with two batteries of different capacities:

1. Unplug AC and let the machine discharge.
2. Open the power panel.
3. The large percentage and the progress bar fill disagree; "Battery size"
   shows one pack's capacity; rate and time-remaining may be `0W` and blank.

Observed on this machine while discharging at ~15 W:

```
$ upower -e | grep BAT
/org/freedesktop/UPower/devices/battery_BAT1
/org/freedesktop/UPower/devices/battery_BAT2

$ omarchy-battery-status --shell
percentage  80%              # aggregate is 70.6%
state       pending-charge   # machine is discharging
rate        0W               # actual draw 15.68 W
size        19Wh             # actual pack 72.81 Wh
time                         # blank; actual ~3.3 h
cycles      86               # BAT1 only; BAT2 is at 129

$ omarchy-battery-status
Battery 80%  ·   left  ·   0W / 19Wh
```

against the kernel's own numbers:

```
BAT1  tablet  19.72 Wh full (23.2 design)  80%  0 W      86 cycles
BAT2  base    53.09 Wh full (62.2 design)  68%  14.66 W  129 cycles

aggregate: 51.37 / 72.81 Wh = 70.6%   draw 15.68 W   ~3.3 h left
```

and against UPower's aggregate device, which the bar icon already uses:

```
$ upower -i /org/freedesktop/UPower/devices/DisplayDevice
    state:               discharging
    energy:              51.85 Wh
    energy-full:         72.81 Wh
    energy-rate:         15.612 W
    time to empty:       3.3 hours
    percentage:          71.2127%
```

## Severity

Cosmetic rather than dangerous: the low-battery notification and the bar icon
both use `UPower.displayDevice`, so there's no risk of a surprise shutdown.
But every number in the panel text is wrong on this hardware, and it reads as
a frozen battery stuck at one percentage drawing 0 W.

## Suggested fix

Sum across every present pack instead of selecting one. Reading `power_now`
from sysfs per pack and adding them preserves the existing trick of keeping
the rate instantaneous where UPower's `energy-rate` lags, and
`UPower.displayDevice` can supply the aggregate state directly.

Worth handling in the same pass:

- packs that expose `charge_*` (uAh) + `voltage_now` rather than `energy_*`
- a pack disappearing at runtime (the SB2 base detaches)
- reporting each pack's `cycle_count`, since they age at different rates

I have a working local version doing this; happy to open a PR if useful.

## System details

- Omarchy 4.0.3-1
- Microsoft Surface Book 2
- Intel Core i7-8650U / UHD Graphics 620 + GeForce GTX 1060 Mobile
- Kernel 7.2.3-arch1-3
- UPower 1.91.3