simple-system-monitor: fix GPU and CPU sensors, CPU usage and network rates

The GPU temperature was read from thermal_zone0, the same motherboard sensor
used for the CPU, so the GPU row showed the CPU value on every install. It is
now read from the GPU itself: nvidia-smi for NVIDIA, hwmon for AMD and Intel.
The CPU sensor is likewise detected rather than defaulting to thermal_zone0,
preferring the on-die package sensor.

CPU usage counted iowait as busy time and left out nice, irq and softirq, so a
slow disk showed as CPU load while real work went uncounted. It is now measured
as the share of time that is neither idle nor waiting on I/O.

Network traffic was summed over every activated interface including loopback and
any VPN, so traffic through a tunnel was counted twice, once on the tunnel and
again on the hardware carrying it. Only physical interfaces are counted now. The
rate itself divided bytes by milliseconds and labelled the result KB, and the
label was missing the per-second part.

The refresh interval becomes a setting, keeping 1 second as the default. GPU
temperature is polled no more than once every 2 seconds since it costs a
subprocess.

The settings object was rebuilt on every settings change while the previous
bindings stayed live, so each change cost more than the one before it.

Author: chloecaffeinexo

simple-system-monitor@ariel/CHANGELOG.md

@@ -1,3 +1,21 @@
+### 1.4.0
+* Read the GPU temperature from the GPU. The default sensor path for both CPU and
+  GPU was thermal_zone0, a motherboard sensor, so the GPU row duplicated the CPU
+  row on every install. NVIDIA cards are read via nvidia-smi, AMD and Intel via
+  their hwmon entries.
+* Detect the CPU sensor rather than defaulting to thermal_zone0, preferring the
+  on-die sensor (coretemp/k10temp package temperature).
+* Fix CPU usage calculation. It counted iowait as busy time and omitted nice, irq
+  and softirq, so a slow disk read as CPU load while real work went uncounted.
+* Count network traffic on physical interfaces only. Loopback, VPN and Tailscale
+  interfaces were included, so traffic through a VPN was counted twice, once on
+  the tunnel and again on the hardware carrying it.
+* Fix network rate units. Bytes were divided by milliseconds and labelled KB, and
+  the per-second part was missing from the label.
+* Add a refresh interval setting, defaulting to the previous 1 second.
+* Only build the settings object once. It was rebuilt on every settings change,
+  leaving the previous bindings live and doubling the work each time.
+
 
 ### 1.3.1
 * Update default scale value to 2