IRQ/9-acpi CPU usage

I found that when my laptop is idle, about 3-4% of the CPU usage is the process `irq/9-acpi` which appears only when auto-cpufreq is active. I confirmed that suspending and restarting the systemd daemon.

A quick investigation with an LLM suggested to try configuring auto-cpufreq to use a shorter polling time, but as far I can tell, I couldn't find any ways to do it.

I would like to first confirm that it is indeed a known auto-cpufreq issue, and if so, how to address it.

Below the output of the debug info on my system from auto-cpufreq..

```
### System information:

-------------------------------- Battery Info ---------------------------------

battery count = 1
BAT0 start threshold = b'75\n'
BAT0 stop threshold = b'80\n'

-------------------------------------------------------------------------------

Linux distro: Debian GNU/Linux 13 trixie
Linux kernel: 6.16.3+deb13-amd64
Processor: Intel(R) Core(TM) Ultra 7 258V
Cores: 8
Architecture: x86_64
Driver: intel_pstate

------------------------------ Current CPU stats ------------------------------

CPU max frequency: 2200 MHz
CPU min frequency: 400 MHz

Core Usage Temperature Frequency
CPU0 1.0% 36 °C 1372 MHz
CPU1 1.0% 37 °C 1069 MHz
CPU2 1.0% 36 °C 1444 MHz
CPU3 0.0% 35 °C 1372 MHz
CPU4 1.0% 36 °C 1651 MHz
CPU5 1.0% 36 °C 400 MHz
CPU6 1.0% 36 °C 1660 MHz
CPU7 0.0% 36 °C 400 MHz

CPU fan speed: 0 RPM

CPU fan speed: 0 RPM

auto-cpufreq version: 2.6.0

Python: 3.13.5
psutil package: 7.0.0
platform package: 1.0.8
click package: 8.3.1
distro package: 1.9.0

Computer type: Notebook
Battery is: discharging

auto-cpufreq system resource consumption:
cpu usage: 0.0 %
memory use: 0.14 %

Total CPU usage: 1.5 %
Total system load: 1.52
Average temp. of all cores: 36.00 °C

Currently using: powersave governor
Currently turbo boost is: off

-------------------------------------------------------------------------------
```

No project file, test, or entry point is named. Start by reproducing the reported 3–4% `irq/9-acpi` usage with auto-cpufreq active and suspended, then compare the daemon and kernel behavior; done means confirming whether this is an auto-cpufreq bug and documenting a supported remedy or the evidence that it is outside the project.

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