ad32fe7a

By: Ammar <ammar.nanjiani@gmail.com>

fix(steammachine): keep the WiFi radio off so it stops competing with Bluetooth

The Steam Machine is wired and has no use for WiFi, but its radio shares an
antenna with the Bluetooth adapter. NetworkManager scans for networks even
while disconnected, and that 2.4 GHz traffic competes with the controller
link — which already suffers from a congested band.

Measured on the running host, with a Pro Controller connected:

                       before      after radio off
  dropped IMU reports   3.2/min     1.5/min
  report gap (delta)    78-105 ms   65-79 ms
  avg_delta             15 ms       11 ms

Adds a oneshot that runs `rfkill block wifi` after NetworkManager starts.

Note the honest ceiling: this halves the loss but does not eliminate it.
The remainder is neighbour congestion — several access points at signal
90-95 on 2.4 GHz (channels 6 and 11 occupied, and this house's own 2.4 GHz
SSID sits on channel 4, which overlaps both). No setting on this host
changes that; eliminating it needs a USB Bluetooth dongle on an extension
cable away from the chassis.

Verified safe before making it declarative: with the WiFi phy soft-blocked,
Bluetooth kept working and improved, and Ethernet stayed connected.

Total

11m55s

Timeline