`omarchy hibernation setup` installs the `keyboard-backlight` system-sleep hook non-executable, so it never runs.

## Cause

The packaged source ships mode 644, and the installer copies it with `cp -p`, faithfully preserving that mode:

```bash
# bin/omarchy-hibernation-setup
sudo cp -p "$OMARCHY_PATH/default/systemd/system-sleep/keyboard-backlight" /usr/lib/systemd/system-sleep/
```

Modes after running the setup:

```
-rw-r--r--  /usr/lib/systemd/system-sleep/keyboard-backlight
-rw-r--r--  /usr/share/omarchy/default/systemd/system-sleep/keyboard-backlight   (omarchy-settings 4.0.0-1)
```

The neighbouring hook, installed correctly, for comparison:

```
-rwxr-xr-x  /usr/lib/systemd/system-sleep/unmount-fuse
```

systemd-sleep(8): "executables in /usr/lib/systemd/system-sleep/ ... All executables in this directory are executed in parallel". A non-executable file there is silently skipped.

## Steps to reproduce

1. `omarchy hibernation setup`
2. `stat -c '%A' /usr/lib/systemd/system-sleep/keyboard-backlight` -> `-rw-r--r--`
3. Hibernate. The keyboard backlight is never turned off, so the hook's purpose (preventing the ASUS keyboard controller from blocking S4) is not served.

## Expected

The hook runs with `pre hibernate` and zeroes the keyboard backlight.

## Suggested fix

Ship `default/systemd/system-sleep/keyboard-backlight` with mode 755, or use `install -m755` instead of `cp -p` in the setup script.

## System

- Omarchy 4.0.0-1, omarchy-settings 4.0.0-1
- systemd 261 (261.2-1-arch), kernel 7.1.8-arch1-3

The visible impact is ASUS-specific, but the hook is inert on every install that runs hibernation setup.