Control Display Backlight?

Hi, how can I control the Raspberry Pad 5's display backlight and power?

I'm on `2022-04-04-raspios-bullseye-arm64-lite` with Kernel 5.15.32-v8+, running KlipperScreen (installed via [kiauh](https://github.com/th33xitus/kiauh))

```
❯ cat /boot/config.txt | grep "^\w"
dtparam=spi=on
dtparam=audio=on
camera_auto_detect=1
display_auto_detect=1
dtoverlay=vc4-kms-v3d
max_framebuffers=2
arm_64bit=1
disable_overscan=1
otg_mode=1
arm_boost=1
dtoverlay=dwc2,dr_mode=host
dtparam=i2c_vc=on
dtoverlay=i2c-rtc,pcf8563,i2c_csi_dsi
```
`/boot/dt-blob.bin` is also installed as per the manual.

A sysfs entry is present:
```
❯ ls /sys/class/backlight/10-0045/
actual_brightness bl_power brightness device max_brightness power scale subsystem type uevent
```
But sending commands has no effect. (using [rpi-backlight](https://github.com/linusg/rpi-backlight)):
`sudo rpi-backlight -p off /sys/class/backlight/10-0045`
Display stays on and at 100% brightness...

Reproduce the issue using the reported Raspberry Pi OS, kernel, /boot/config.txt, and installed /boot/dt-blob.bin. Inspect /sys/class/backlight/10-0045 and the rpi-backlight command, then determine and document a working way to control the display brightness and power.

Written by the indexing model from the issue text.